user912: I've recently become interested in infinite chess (this presentation from Joel David Hamkins [updated presentation based on the link provided by JDH in comments; significantly more comprehensive than what was originally linked to] talks a bit about it and some of the interesting mathematical questions). You can find another discussion of the mathematical properties of infinite chess here.
My question is, has this variant been much explored by chess players (as opposed to mathematicians, not that they aren't also chess players)? Are there resources that explain the strategy for infinite chess? Do the principles that guide standard chess play change drastically for the infinite variant, or are they merely extended?

user7002: I think this is a valid 2-Rook mate on an infinite board. You use one rook as the wall and the other rook to cooperate with K to give KR vs K mate conventionally.
[FEN "2R5/3k4/8/8/8/8/8/4R2K w - - 0 1"]

1. Ree8 Kd6 2. Kg2 Kd5 3. Kf3 Kd4 4. Re7 Kd5 5. Kf4 Kd6 6. Rcc7 Kd5
7. Red7+ Ke6 8. Rb7 Kf6 9. Rb6# 1-0


user924: All the normal rules of chess strategy must be completely void. Consider some of the most important ones:

Material advantage helps to win. Mainly because with more material it's easier to queen a pawn (not available in infinite chess) and because it makes it easier to checkmate the other king. But checkmate is much harder anyway (no board edge to help), and in infinite chess you may have a billion extra knights that are of no use to help defend your king because they're a trillion squares over to the left. In general material will still be useful, but I doubt a queen is going to be much better than a rook.
The center. In chess, pieces want to be placed where they influence the most squares, and that's usually the center. In infinite chess, there is no center and no square is inherintly better than any other.
Development. There is no starting position, and no concept of a square that's better than the original square, so no development.
Pawn structure is an artifact of having two rows of 8 pawns at the start, and a center. Without any of that, all the knowledge we have about pawn structure goes out the window. A pawn may advance a billion squares without ever meeting another pawn, or be blocked by a trillion of them.

And so on, and so on.
I think a study of the strategy of infinite chess would have to start with an analysis of which basic mates are possible (queen, rook and king vs king probably mates, two rooks don't, I guess? Definitely a lone queen and king doesn't, needs an edge).
If you have a lot of pieces, you'd think you'd want to move part of them towards the enemy king, keeping some at home to defend the king. But for queens, rooks and bishops, distances are deceptive -- if the lines and diagonals are clear, they can get to wherever they can possibly get in two moves. Pawns, kings and knights are unimaginably useless in comparison.
I wonder if anything is known about games of infinite chess with more than a few pieces.

user3454: Thank you for the question, and for linking to some of my work on infinite chess. You can find additional material on infinite chess on my blog at http://jdh.hamkins.org/tag/infinite-chess/. There are numerous talks, including slides, with infinite chess movies, as well as more detailed research papers and more. I'd be happy to discuss any aspect of that---please go ahead and ask focussed questions about infinite chess. 
But in regards to your question, I would agree that most people working on infinite chess are more mathematicians than chess players, and furthermore the central issues seem to be mathematical in nature. Certainly I am more a mathematician than a chess player, although I enjoy a lot of chess (you can play me on ICC, username: JDH). 
You ask specifically whether infinite chess has been explored by chess players, as opposed to mathematicians, and the answer to this is yes. My co-author on several of the infinite chess papers, for example, is C. D. A. Evans, US National master, also philosophy PhD candidate at the City University of New York, but not a mathematician. Also, Noam Elkies, professor at Harvard, is also an accomplished chess player who is also a mathematician, and has written on infinite chess.  
In my research practice with Cory Evans, I can report that his chess intuition and analysis was invaluable in shooting down and finding flaws in numerous proposed chess positions. But also, it seemed to be an essentially mathematical activity to come up with the various infinite chess positions that illustrate the various high game values and so on. So it was a true collaboration between two fields.

912: <p>I've recently become interested in infinite chess (this <a href="http://jdh.hamkins.org/transfinite-game-values-in-infinite-chess-bonn-january-2017/" rel="nofollow noreferrer">presentation from Joel David Hamkins</a> [updated presentation based on the link provided by JDH in comments; significantly more comprehensive than what was originally linked to] talks a bit about it and some of the interesting mathematical questions). You can find another discussion of the mathematical properties of infinite chess <a href="https://mathoverflow.net/questions/27967/decidability-of-chess-on-an-infinite-board">here</a>.</p>

<p>My question is, has this variant been much explored by chess players (as opposed to mathematicians, not that they aren't also chess players)? Are there resources that explain the strategy for infinite chess? Do the principles that guide standard chess play change drastically for the infinite variant, or are they merely extended?</p>
 7002: <p>I think this is a valid 2-Rook mate on an infinite board. You use one rook as the wall and the other rook to cooperate with K to give KR vs K mate conventionally.</p>

<pre><code>[FEN "2R5/3k4/8/8/8/8/8/4R2K w - - 0 1"]

1. Ree8 Kd6 2. Kg2 Kd5 3. Kf3 Kd4 4. Re7 Kd5 5. Kf4 Kd6 6. Rcc7 Kd5
7. Red7+ Ke6 8. Rb7 Kf6 9. Rb6# 1-0
</code></pre>
 924: <p>All the normal rules of chess strategy must be completely void. Consider some of the most important ones:</p>

<ul>
<li><p>Material advantage helps to win. Mainly because with more material it's easier to queen a pawn (not available in infinite chess) and because it makes it easier to checkmate the other king. But checkmate is much harder anyway (no board edge to help), and in infinite chess you may have a billion extra knights that are of no use to help defend your king because they're a trillion squares over to the left. In general material will still be useful, but I doubt a queen is going to be much better than a rook.</p></li>
<li><p>The center. In chess, pieces want to be placed where they influence the most squares, and that's usually the center. In infinite chess, there is no center and no square is inherintly better than any other.</p></li>
<li><p>Development. There is no starting position, and no concept of a square that's better than the original square, so no development.</p></li>
<li><p>Pawn structure is an artifact of having two rows of 8 pawns at the start, and a center. Without any of that, all the knowledge we have about pawn structure goes out the window. A pawn may advance a billion squares without ever meeting another pawn, or be blocked by a trillion of them.</p></li>
</ul>

<p>And so on, and so on.</p>

<p>I think a study of the strategy of infinite chess would have to start with an analysis of which basic mates are possible (queen, rook and king vs king probably mates, two rooks don't, I guess? Definitely a lone queen and king doesn't, needs an edge).</p>

<p>If you have a lot of pieces, you'd think you'd want to move part of them towards the enemy king, keeping some at home to defend the king. But for queens, rooks and bishops, distances are deceptive -- if the lines and diagonals are clear, they can get to wherever they can possibly get in two moves. Pawns, kings and knights are unimaginably useless in comparison.</p>

<p>I wonder if anything is known about games of infinite chess with more than a few pieces.</p>
 3454: <p>Thank you for the question, and for linking to some of my work on infinite chess. You can find additional material on infinite chess on my blog at <a href="http://jdh.hamkins.org/tag/infinite-chess/" rel="nofollow noreferrer">http://jdh.hamkins.org/tag/infinite-chess/</a>. There are numerous talks, including slides, with infinite chess movies, as well as more detailed research papers and more. I'd be happy to discuss any aspect of that---please go ahead and ask focussed questions about infinite chess. </p>

<p>But in regards to your question, I would agree that most people working on infinite chess are more mathematicians than chess players, and furthermore the central issues seem to be mathematical in nature. Certainly I am more a mathematician than a chess player, although I enjoy a lot of chess (you can play me on ICC, username: JDH). </p>

<p>You ask specifically whether infinite chess has been explored by chess players, as opposed to mathematicians, and the answer to this is yes. My co-author on several of the infinite chess papers, for example, is <a href="http://www.uschess.org/msa/MbrDtlMain.php?12565771" rel="nofollow noreferrer">C. D. A. Evans</a>, US National master, also philosophy PhD candidate at the City University of New York, but not a mathematician. Also, <a href="http://math.harvard.edu/~elkies/chess.html" rel="nofollow noreferrer">Noam Elkies</a>, professor at Harvard, is also an accomplished chess player who is also a mathematician, and has written on infinite chess.  </p>

<p>In my research practice with Cory Evans, I can report that his chess intuition and analysis was invaluable in shooting down and finding flaws in numerous proposed chess positions. But also, it seemed to be an essentially mathematical activity to come up with the various infinite chess positions that illustrate the various high game values and so on. So it was a true collaboration between two fields.</p>
