user390: I am trying to train tactics as well as my general understanding of the beginning/middlegame. I spent a good bit of time understanding endgames, per chessmaster recommendations and those I can understand.
As far as tactics, I have been able to "train" them through chesstempo.com and "see" lots of variations through chesstactics.org. 
But how do I learn to understand what I am training? I feel like I can execute tactics now without thinking, but I am not really sure what I just did. It just "feels right" because I trained it.
So what I am really asking:

Is there a good place to get a real understanding of the middle game, or is it just raw calculation? Maybe I am missing a positional understanding?

I am thinking about getting a chess.com membership and going through the chess mentor courses. 
I feel like by just doing raw training I am missing out on the real soul of the game.

user19861: Both Silman's books and Nimzo's My System are must reads once you've reached about 1900 and are looking to take your game to the next level. 
If you're below 1900 trying to understand positional play is like doing calculus without understanding basic addition and subtraction. Tactics are the fundamentals of chess. Nothing else will make sense without a strong understanding of tactics. 

user2001: Major edit (no intro, just straight to the point):

Is there a good place to get a real understanding of the middle game,
  or is it just raw calculation? Maybe I am missing a positional
  understanding?

Raw calculation does not exist. Every calculation of a position will lead to a final position that needs to be evaluated. A position can be evaluated from many different points of view. The two major views are "positional" and "dynamic". The positional view focuses on the static aspects of the position, like a snap shot of the position. The dynamic view focuses on the dynamic possibilities in the position.
Dividing a game into the opening, middlegame and endgame does not always help to understand chess better. After all, any position can be evaluated using one or more evaluation strategies that exist today. Thus, understanding the middlegame means understanding positions where most of the pieces are still on the board.
Based on my own subjective view, positional understanding is harder to master than dynamic understanding. Perhaps because combinations are so tempting and beautiful. Still, some players find positional thinking easier than dynamic thinking. Those players have huge issues with messy positions where several pieces are hanging. Thus, to handle positions where most pieces are still on the board, a player needs to master both positional and dynamic reasoning.
The short answer would actually be: good books, good trainers and many over the board games against slightly stronger opponents!

user2339: Training with different opening and middle game position will slowly teach you to understand. It like learning to play a guitar, etc. It takes time to learn. By using different positions you will learn how to find weak spots and so on. But of course there are books that will give you a better understanding.
Here are some: 

John Nunn: Understand the middle game
John Nunn: Learn chess tactics
Artur Yusupov: there are 9 books here. GET THEM!!!

Also, find a friend that is just a bit better than you, and if you don't have a friend that play's chess, sign yourself up in a chess club, and find a player that is a bit better than you. Use this person to play around in different opening positions, and learn from them. It is important to write down your game so you can analyze the positions and where you go wrong. By doing this you will improve.
In a chess club you will possibly find players that you can beat with no problem, but also probably find players that you can't beat. Let's say that you move yourself up to 1450 in rating, now you should find a player around 1550 - 1600. Learn from this person, and slowly you start to get draws and eventually start to win, and at the end beat the player. Use a bit of time in that rating group, and when you feel ready, find a new player at 1650-1700, learn from this player and so on. If you do this seriously you can move yourself up to a rating around 1900-2100 within 1-2 years. Good luck!

user7646: I recently read an unrelated book (I think it's Thinking, fast and slow, which is an excellent book), but one part of the book cited some studies done on chess players.
For example: to detect supposed superior intellect, there was only a slightly elevated level of intelligence associated with the players in general and the single most important factor in determining the success of a player was experience rather than innate cognitive abilities.
Essentially, because the player accumulates a largely subconscious appreciation of common openings, positions and mistakes etc., this reduces the amount of time they need to spend looking at the "common" moves in any situation and allow them to start calculating at a deeper level.
On average, the raw ability to calculate moves is not particularly lacking or abundant in poor or good players, so in a way this is good as you might be able to make it to grandmaster but the bad news is you may need to set aside 23 hours a day to practice.
On a side note, the main thrust of the story was about determining the sex of chickens; it takes 3 years to learn how to determine the sex of a chick which once qualified they do in a fraction of a second but are unable to say how they can do it other than that it "feels right".

user11245: There are 3 basic themes in middlegame planning:

 Pawn breaks to 

Create open files
Seize control of the center
Eliminate pawns that control key squares


 Short plans to create a positional imbalance, e.g.:

Set up an outpost
Create doubled, backward or isolated pawns in your opponent's pawn structure
Weaken the king's position
Sideline or block-in an opponent's piece
Redeploy one of your pieces to a better square
Seize control of a key file or diagonal
Exchange off a poor minor piece of your own for a better piece of your opponent's


Preparing for transition to the endgame, involving:

Trading or preserving either one pair or both pairs of rooks
Selecting which minor piece(s) of your own to keep and which of your opponent's to eliminate to maximize the imbalance of material based on the deployment of the remaining pawns
Deploying your remaining pieces and king so they're in position and ready for the transition
Adjusting your pawns for optimal placement for the type of endgame you're seeking

As you can tell, the pawn structure is the focus of many of these elements. For more on how to plan regarding the pawn structures that arise from common openings, take a look at my response to another question, Middlegame Plans.

user70: By definition, the middle game is the point in the game where the pieces are pretty much developed and the opening ends.
The middle game is not raw calculation. Calculation is just a skill we have to develop. The middle game is not just tactics, though tactical opportunities begin to present themselves in the middle game.
At the beginning of the middle game, you start to formulate a plan and execute it.  Without a plan, you won't know where to point your pieces and what you're trying to accomplish.  When you see a 'tactics trainer' puzzle, what you're seeing is the fruit of planning.  Those piece sacs and amazing moves didn't happen randomly; someone made the situation possible.  That's what you're doing in the middle game.
An inability to plan is one of my greatest faults - I'm so unimaginative that I can't formulate a plan.  Therefore I am always end up playing defensively.  Now, I calculate pretty well for my category, so when someone attacks me (that is, they formulate a plan and execute it, lol) I frequently gain an advantage and get the win.

user419: Excellent question and you made a good assumption.

I feel like I can execute tactics now without thinking, but I am not really sure what I just did.
Maybe I am missing a positional understanding?

That's exactly what you are missing, because tactics are the consequence of good positional understanding (this is a startling claim, feel free to disagree!).
I'd like to recommend you some books to study for improving the middlegame.
"Think like a grandmaster" by Alexander Kotov concentrates on middlegame aspects. This book "feels" lightweight since it's very easy to read, yet I'd like to conventionally call it "middlegame strategy lessons for dummies", because Kotov often quotes Steinitz (who pioneered the positional approach) yet explains his postulates in a way that's understandable by the average chess player, not only by grandmasters.
"My System" and "My System In Practice" by Aron Nimzowitsch. These two books are widely acknowledged by many strong chess players as being the greatest chess manual ever. There's a shorter work of Nimzowitsch that literally translates from Russian as "How I became a grandmaster". It's a short chess centric biography which describes the early Nimzowitsch as a strong tactical player who totally lacked positional understanding. Just like you, he would "see" combinations, but couldn't explain why they are possible. He tried to play in some tournaments against masters and failed, so he took a break trying to understand what's going on. And his deep understanding of strategy came from "scratching the positional itch".

user109: I think you partially answered your question.  The main fact that you can "...execute tactics now without thinking..." is definitely a good start.  Also that fact that you said, it "feels right" is also a good start although you don't really want to play a tactic just because it "feels right".
Information on tactics can be found from Louis Holtzhausen site at http://www.chess-strategies-tactics.com/chess-tactics. Here is some information from that site:
Understanding why you would do a particular tactic can be made simple by the definition:

A Chess tactic is a move or a combination of moves whereby you force
  an advantage.  The advantage is usually to win material but it could
  also be to achieve a positional advantage.

I think the fact that you said you can make tactical moves without thinking much means that you have improved your chess tactical awareness.
You can solve 1000's of tactical puzzles, but with no overall view of the specific skills you are trying to improve, solving them is not as effective.  The 3 main focus areas of training chess tactics skill are:
1. Tactical patterns(how is the tactic executed)
2. Tactical themes(which elements of the position made the tactics possible)
3. Tactical awareness(knowing when to search for a tactical combination)

I think for each tactics puzzle that you do, before you do the next puzzle you must have a deep understanding of 1) themes and 2) patterns that made the tactics possible in the puzzle.
See if you can figure out which aspects of the position actually made the combination possible.  This style of tactics training will hone your "tactical awareness".
Here are tactical themes and patterns that you should be familiar with.
You can find many of these themes on chess tempos website here
Fork or double attack
Pins and skewers  
Sacrifice  
Discovered attack  
Deflection (or distraction)  
Double check  
Counter-attack  
Hanging (undefended) piece  
Exposed king  
In-between move  
Trapped piece  
Clearance – Opening a critical square, file or diagonal  
Blocking – blocking a critical file or diagonal  
Advanced pawn  
Attraction  
Zugzwang  
X-ray attack  
Weak back rank  
Removing the defender  
Overloading a defender  
Simplification into a winning endgame  
Indirect defense  
Domination in chess  

Here are checkmate patterns you should be familiar with.
Checkmate pattern details can be found here.
Back Rank checkmate
Lolli’s checkmate
Epaulettes checkmate
Shepherd’s checkmate
Fool’s checkmate (fool’s mate or 2-move checkmate)
Scholar’s checkmate ( or 4-move checkmate)
Two Rooks checkmate
Mayet’s checkmate
Smothered checkmate
Anderssen’s checkmate
Pillsbury’s checkmate
The Arabian checkmate
Legal’s checkmate
Anastacia’s checkmate
Greco’s checkmate
Gueridon’s checkmate
Blackburne’s checkmate
Boden’s checkmate
Damiano’s checkmate

Understanding the tactical themes is useful… but training your mind to recognize the theme instantly and apply it in your game is only possible once you have turned your understanding into a skill. So how do you turn your understanding into a skill? Practice, practice, practice. Practice till you can apply your understanding almost without thinking.
Even if you find the content on these chess tactics themes and patterns obvious – it won’t do any harm to go over it again. It is vital to make this knowledge your second nature. It is better to understand a few patterns deeply than to understand many patterns superficially. Patterns you understand deeply will be much easier to apply!
Here are some tactical articles that  will help you with tactics in the middle game:
http://www.kenilworthchessclub.org/links/middlegame.html

user167: In principle, the middlegame is indeed just raw calculation. In principle, the entire game of chess boils down to only that. But since the space of possible move sequences is so vast, chess is of course too complex from the standpoint of pure calculation for that to be all that we do when we play. And after all, even our computational superiors (chess engines) need to be guided with built-in positional understanding in order to play a good game of chess.
So yes, if you're feeling fairly comfortable with your grasp of calculation and the execution of tactical operations, but often find yourself "not really sure what [you] just did," then it does sound like positional understanding is what you need to accrue. A good way to look at things is this: tactics are a means to an end - and at bottom they are the means to all ends in chess - but it's not terribly useful to see tactics as the ends themselves, and that is where heuristic positional knowledge is most useful, as a guide telling you what purposes various tactics should be put toward.
For instance, former champion Vladimir Kramnik described the play of two of his predecessors thus:

To a certain extent, Smyslov was the pioneer of this style, which was later brilliantly developed by Karpov, i.e. the gradual mounting of positional pressure based on the most accurate calculation of short lines.

Now, regardless of whether you want to play like a Smyslov or Karpov, or more like an Alekhine or Tal, I point to Kramnik's words here just because they bring out this idea of letting positional considerations guide your hand, while your tactical acumen gives you the wherewithal to achieve your aims. OK, so how to acquire positional understanding?
Here there are many many options. You mention chess.com's chess mentor course; I have no knowledge of that, and so have no opinion. I can point you to a couple of books that are designed to begin to steer amateurs toward an expert/master understanding of positional play:

How to Reassess Your Chess by Jeremy Silman. This is perhaps the most widely-known book on the subject these days, and with good reason I think. Silman does a fine job of getting the reader to (1) look at positions through the lens of various types of imbalances - e.g. who has more space, is one side's bishop better than the other's, is one king safer than the other's, etc. - and (2) begin to use those imbalances as guiding factors in determining what your plan/goals should be - e.g. I have two bishops against two knights, so I'd like to open up the position to make use of the bishops' long-range power.
The Giants of Strategy by Neil McDonald. This book is less systematically instructional than Silman's, but it is still instructive. McDonald looks at examples of play from Kramnik, Karpov, Petrosian, Capablanca and Nimzowitsch in chapters grouped around positional themes (e.g. the seventh rank, outposts, pawn breaks, planning). This isn't an overly advanced book, and is probably well-suited to the same audience as Silman's. I wouldn't recommend this book alone for gaining positional understanding, but I think it can act very nicely as a supplement to Silman, say. 


390: <p>I am trying to train tactics as well as my general understanding of the beginning/middlegame. I spent a good bit of time understanding endgames, per chessmaster recommendations and those I can understand.</p>

<p>As far as tactics, I have been able to "train" them through chesstempo.com and "see" lots of variations through chesstactics.org. </p>

<p>But how do I learn to understand what I am training? I feel like I can execute tactics now without thinking, but I am not really sure what I just did. It just "feels right" because I trained it.</p>

<p>So what I am really asking:</p>

<blockquote>
  <p>Is there a good place to get a real understanding of the middle game, or is it just raw calculation? Maybe I am missing a positional understanding?</p>
</blockquote>

<p>I am thinking about getting a chess.com membership and going through the chess mentor courses. </p>

<p>I feel like by just doing raw training I am missing out on the real soul of the game.</p>
 19861: <p>Both Silman's books and Nimzo's My System are must reads once you've reached about 1900 and are looking to take your game to the next level. </p>

<p>If you're below 1900 trying to understand positional play is like doing calculus without understanding basic addition and subtraction. Tactics are the fundamentals of chess. Nothing else will make sense without a strong understanding of tactics. </p>
 2001: <p>Major edit (no intro, just straight to the point):</p>

<blockquote>
  <p>Is there a good place to get a real understanding of the middle game,
  or is it just raw calculation? Maybe I am missing a positional
  understanding?</p>
</blockquote>

<p>Raw calculation does not exist. Every calculation of a position will lead to a final position that needs to be evaluated. A position can be evaluated from many different points of view. The two major views are "positional" and "dynamic". The positional view focuses on the static aspects of the position, like a snap shot of the position. The dynamic view focuses on the dynamic possibilities in the position.</p>

<p>Dividing a game into the opening, middlegame and endgame does not always help to understand chess better. After all, any position can be evaluated using one or more evaluation strategies that exist today. Thus, understanding the middlegame means understanding positions where most of the pieces are still on the board.</p>

<p>Based on my own subjective view, positional understanding is harder to master than dynamic understanding. Perhaps because combinations are so tempting and beautiful. Still, some players find positional thinking easier than dynamic thinking. Those players have huge issues with messy positions where several pieces are hanging. Thus, to handle positions where most pieces are still on the board, a player needs to master both positional and dynamic reasoning.</p>

<p>The short answer would actually be: good books, good trainers and many over the board games against slightly stronger opponents!</p>
 2339: <p>Training with different opening and middle game position will slowly teach you to understand. It like learning to play a guitar, etc. It takes time to learn. By using different positions you will learn how to find weak spots and so on. But of course there are books that will give you a better understanding.
Here are some: </p>

<ul>
<li>John Nunn: Understand the middle game</li>
<li>John Nunn: Learn chess tactics</li>
<li>Artur Yusupov: there are 9 books here. GET THEM!!!</li>
</ul>

<p>Also, find a friend that is just a bit better than you, and if you don't have a friend that play's chess, sign yourself up in a chess club, and find a player that is a bit better than you. Use this person to play around in different opening positions, and learn from them. It is important to write down your game so you can analyze the positions and where you go wrong. By doing this you will improve.</p>

<p>In a chess club you will possibly find players that you can beat with no problem, but also probably find players that you can't beat. Let's say that you move yourself up to 1450 in rating, now you should find a player around 1550 - 1600. Learn from this person, and slowly you start to get draws and eventually start to win, and at the end beat the player. Use a bit of time in that rating group, and when you feel ready, find a new player at 1650-1700, learn from this player and so on. If you do this seriously you can move yourself up to a rating around 1900-2100 within 1-2 years. Good luck!</p>
 7646: <p>I recently read an unrelated book (I think it's <em>Thinking, fast and slow</em>, which is an excellent book), but one part of the book cited some studies done on chess players.</p>

<p>For example: to detect supposed superior intellect, there was only a slightly elevated level of intelligence associated with the players in general and the single most important factor in determining the success of a player was <em>experience</em> rather than <em>innate cognitive abilities</em>.</p>

<p>Essentially, because the player accumulates a largely subconscious appreciation of common openings, positions and mistakes etc., this reduces the amount of time they need to spend looking at the "common" moves in any situation and allow them to start calculating at a deeper level.</p>

<p>On average, the raw ability to calculate moves is not particularly lacking or abundant in poor or good players, so in a way this is good as you might be able to make it to grandmaster but the bad news is you may need to set aside 23 hours a day to practice.</p>

<p>On a side note, the main thrust of the story was about determining the sex of chickens; it takes 3 years to learn how to determine the sex of a chick which once qualified they do in a fraction of a second but are unable to say how they can do it other than that it "feels right".</p>
 11245: <p>There are 3 basic themes in middlegame planning:</p>

<ol>
<li> Pawn breaks to </li>
<ul>
<li>Create open files</li>
<li>Seize control of the center</li>
<li>Eliminate pawns that control key squares</li>
</ul>
<br>
<li> Short plans to create a positional imbalance, e.g.:</li>
<ul>
<li>Set up an outpost</li>
<li>Create doubled, backward or isolated pawns in your opponent's pawn structure</li>
<li>Weaken the king's position</li>
<li>Sideline or block-in an opponent's piece
<li>Redeploy one of your pieces to a better square</li>
<li>Seize control of a key file or diagonal</li>
<li>Exchange off a poor minor piece of your own for a better piece of your opponent's</li>
</ul>
<br>
<li>Preparing for transition to the endgame, involving:</li>
<ul>
<li>Trading or preserving either one pair or both pairs of rooks</li>
<li>Selecting which minor piece(s) of your own to <i>keep</i> and which of your opponent's to <i>eliminate</i> to maximize the imbalance of material based on the deployment of the remaining pawns</li>
<li>Deploying your remaining pieces and king so they're in position and ready for the transition</li>
<li>Adjusting your pawns for optimal placement for the type of endgame you're seeking</li>
</ul>
</ol>

<p>As you can tell, the pawn structure is the focus of many of these elements. For more on how to plan regarding the pawn structures that arise from common openings, take a look at my response to another question, <a href="https://chess.stackexchange.com/questions/15481/middlegame-plans/15485#15485"><em>Middlegame Plans</em></a>.</p>
 70: <p>By definition, the middle game is the point in the game where the pieces are pretty much developed and the opening ends.</p>

<p>The middle game is <strong>not</strong> raw calculation. Calculation is just a skill we have to develop. The middle game is <strong>not</strong> just tactics, though tactical opportunities begin to present themselves in the middle game.</p>

<p>At the beginning of the middle game, you start to <strong>formulate a plan</strong> and <strong>execute it</strong>.  Without a plan, you won't know where to point your pieces and what you're trying to accomplish.  When you see a 'tactics trainer' puzzle, what you're seeing is the fruit of planning.  Those piece sacs and amazing moves didn't happen randomly; someone made the situation possible.  That's what you're doing in the middle game.</p>

<p>An inability to plan is one of my greatest faults - I'm so unimaginative that I can't formulate a plan.  Therefore I am always end up playing defensively.  Now, I calculate pretty well for my category, so when someone attacks me (that is, they formulate a plan and execute it, lol) I frequently gain an advantage and get the win.</p>
 419: <p>Excellent question and you made a good assumption.</p>
<blockquote>
<p>I feel like I can execute tactics now without thinking, but I am not really sure what I just did.</p>
<p>Maybe I am missing a positional understanding?</p>
</blockquote>
<p>That's exactly what you are missing, because tactics are the consequence of good positional understanding (this is a startling claim, feel free to disagree!).</p>
<p>I'd like to recommend you some books to study for improving the middlegame.</p>
<p>&quot;Think like a grandmaster&quot; by Alexander Kotov concentrates on middlegame aspects. This book &quot;feels&quot; lightweight since it's very easy to read, yet I'd like to conventionally call it &quot;middlegame strategy lessons for dummies&quot;, because Kotov often quotes Steinitz (who pioneered the positional approach) yet explains his postulates in a way that's understandable by the average chess player, not only by grandmasters.</p>
<p>&quot;My System&quot; and &quot;My System In Practice&quot; by Aron Nimzowitsch. These two books are widely acknowledged by many strong chess players as being the greatest chess manual ever. There's a shorter work of Nimzowitsch that literally translates from Russian as &quot;How I became a grandmaster&quot;. It's a short chess centric biography which describes the early Nimzowitsch as a strong tactical player who totally lacked positional understanding. Just like you, he would &quot;see&quot; combinations, but couldn't explain why they are possible. He tried to play in some tournaments against masters and failed, so he took a break trying to understand what's going on. And his deep understanding of strategy came from &quot;scratching the positional itch&quot;.</p>
 109: <p>I think you partially answered your question.  The main fact that you can "...execute tactics now without thinking..." is definitely a good start.  Also that fact that you said, it "feels right" is also a good start although you don't really want to play a tactic just because it "feels right".</p>

<p>Information on tactics can be found from <code>Louis Holtzhausen</code> site at <a href="http://www.chess-strategies-tactics.com/chess-tactics">http://www.chess-strategies-tactics.com/chess-tactics</a>. Here is some information from that site:</p>

<p>Understanding why you would do a particular tactic can be made simple by the definition:</p>

<blockquote>
  <p>A Chess tactic is a move or a combination of moves whereby you force
  an advantage.  The advantage is usually to win material but it could
  also be to achieve a positional advantage.</p>
</blockquote>

<p>I think the fact that you said you can make tactical moves without thinking much means that you have improved your chess tactical awareness.</p>

<p>You can solve 1000's of tactical puzzles, but with no overall view of the specific skills you are trying to improve, solving them is not as effective.  The 3 main focus areas of training chess tactics skill are:</p>

<pre><code>1. Tactical patterns(how is the tactic executed)
2. Tactical themes(which elements of the position made the tactics possible)
3. Tactical awareness(knowing when to search for a tactical combination)
</code></pre>

<p>I think for each tactics puzzle that you do, before you do the next puzzle you must have a deep understanding of <code>1) themes</code> and <code>2) patterns</code> that made the tactics possible in the puzzle.</p>

<p>See if you can figure out which aspects of the position actually made the combination possible.  This style of tactics training will hone your "tactical awareness".</p>

<p>Here are tactical themes and patterns that you should be familiar with.
You can find many of these themes on chess tempos website <a href="http://chesstempo.com/tactical-motifs.html">here</a></p>

<pre><code>Fork or double attack
Pins and skewers  
Sacrifice  
Discovered attack  
Deflection (or distraction)  
Double check  
Counter-attack  
Hanging (undefended) piece  
Exposed king  
In-between move  
Trapped piece  
Clearance – Opening a critical square, file or diagonal  
Blocking – blocking a critical file or diagonal  
Advanced pawn  
Attraction  
Zugzwang  
X-ray attack  
Weak back rank  
Removing the defender  
Overloading a defender  
Simplification into a winning endgame  
Indirect defense  
Domination in chess  
</code></pre>

<p>Here are checkmate patterns you should be familiar with.
Checkmate pattern details can be found <a href="http://en.wikipedia.org/wiki/Checkmate_pattern">here</a>.</p>

<pre><code>Back Rank checkmate
Lolli’s checkmate
Epaulettes checkmate
Shepherd’s checkmate
Fool’s checkmate (fool’s mate or 2-move checkmate)
Scholar’s checkmate ( or 4-move checkmate)
Two Rooks checkmate
Mayet’s checkmate
Smothered checkmate
Anderssen’s checkmate
Pillsbury’s checkmate
The Arabian checkmate
Legal’s checkmate
Anastacia’s checkmate
Greco’s checkmate
Gueridon’s checkmate
Blackburne’s checkmate
Boden’s checkmate
Damiano’s checkmate
</code></pre>

<p>Understanding the tactical themes is useful… but training your mind to recognize the theme instantly and apply it in your game is only possible once you have turned your understanding into a skill. So how do you turn your understanding into a skill? Practice, practice, practice. Practice till you can apply your understanding almost without thinking.</p>

<p>Even if you find the content on these chess tactics themes and patterns obvious – it won’t do any harm to go over it again. It is vital to make this knowledge your second nature. It is better to understand a few patterns deeply than to understand many patterns superficially. Patterns you understand deeply will be much easier to apply!</p>

<p>Here are some tactical articles that  will help you with tactics in the middle game:
<a href="http://www.kenilworthchessclub.org/links/middlegame.html">http://www.kenilworthchessclub.org/links/middlegame.html</a></p>
 167: <p><em>In principle</em>, the middlegame is indeed just raw calculation. In principle, the entire game of chess boils down to only that. But since the space of possible move sequences is so vast, chess is of course too complex from the standpoint of pure calculation for that to be all that we do when we play. And after all, even our computational superiors (chess engines) need to be guided with built-in positional understanding in order to play a good game of chess.</p>

<p>So yes, if you're feeling fairly comfortable with your grasp of calculation and the execution of tactical operations, but often find yourself "not really sure what [you] just did," then it does sound like positional understanding is what you need to accrue. A good way to look at things is this: tactics are a means to an end - and at bottom they are <em>the means to all ends</em> in chess - but it's not terribly useful to see tactics as the ends themselves, and that is where heuristic positional knowledge is most useful, as a guide telling you what purposes various tactics should be put toward.</p>

<p>For instance, former champion Vladimir Kramnik described the play of two of his predecessors thus:</p>

<blockquote>
  <p>To a certain extent, Smyslov was the pioneer of this style, which was later brilliantly developed by Karpov, i.e. the gradual mounting of positional pressure based on the most accurate calculation of short lines.</p>
</blockquote>

<p>Now, regardless of whether you want to play like a Smyslov or Karpov, or more like an Alekhine or Tal, I point to Kramnik's words here just because they bring out this idea of letting positional considerations guide your hand, while your tactical acumen gives you the wherewithal to achieve your aims. OK, so how to acquire positional understanding?</p>

<p>Here there are many many options. You mention chess.com's chess mentor course; I have no knowledge of that, and so have no opinion. I can point you to a couple of books that are designed to begin to steer amateurs toward an expert/master understanding of positional play:</p>

<ul>
<li><p><em>How to Reassess Your Chess</em> by Jeremy Silman. This is perhaps the most widely-known book on the subject these days, and with good reason I think. Silman does a fine job of getting the reader to (1) look at positions through the lens of various types of <em>imbalances</em> - e.g. who has more space, is one side's bishop better than the other's, is one king safer than the other's, etc. - and (2) begin to use those imbalances as guiding factors in determining what your plan/goals should be - e.g. I have two bishops against two knights, so I'd like to open up the position to make use of the bishops' long-range power.</p></li>
<li><p><em>The Giants of Strategy</em> by Neil McDonald. This book is less systematically instructional than Silman's, but it is still instructive. McDonald looks at examples of play from Kramnik, Karpov, Petrosian, Capablanca and Nimzowitsch in chapters grouped around positional themes (e.g. the seventh rank, outposts, pawn breaks, planning). This isn't an overly advanced book, and is probably well-suited to the same audience as Silman's. I wouldn't recommend this book alone for gaining positional understanding, but I think it can act very nicely as a supplement to Silman, say. </p></li>
</ul>
