user2984: Once when I was reading a book from Kasparov he quoted that most of the modern ideas in the semi-Slav came from Larsen games. Does anyone know good novelties that Larsen brings in this opening?   

user1485: Kasparov in My Great Predecessors, Part 4:

Generally speaking, Larsen's contribution to the development of opening theory is not very great, since usually he aimed to lure his opponents into little-studied variations and mainly relied on his skill in the middlegame. Nevertheless, he played a key role in the development of what is currently one of the most popular lines in the Semi-Slav Defence, the so-called improved Meran Variation: 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 e6 5 e3 Nbd7 6. Bd3 dc4 7.Bc4 b5 8.Bd3 Bb7!?

One of Larsen's ideas was to allow a check on b5 and give up castling rights. In return he got a strong knight on d5. He first used this idea in the Candidate match Ivkov-Larsen 1965, see game below. Read more about it here.
Sample games:
  [FEN ""]
  [Event "Larsen-Ivkov Candidates Quarterfinal Match"]
  [Site "Bled YUG"]
  [Date "1965.07.05"]
  [EventDate "1965.06.27"]
  [Round "6"]
  [Result "1/2-1/2"]
  [White "Borislav Ivkov"]
  [Black "Bent Larsen"]
  
  1.c4 Nf6 2.Nc3 e6 3.Nf3 d5 4.d4 c6 5.e3 Nbd7 6.Bd3 dxc4 7.Bxc4
  b5 8.Bd3 Bb7 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Bxc5 13.dxc5
  Nxc5 14.Bb5+ Kf8 15.Qd4 Qb6 16.Be2 h6 17.O-O g6 18.Bd2 Kg7
  19.Rac1 Rac8 20.Qh4 g5 21.Qg4 Ne4 22.Rxc8 Rxc8 23.Qxe4 Nf4
  24.Qe3 Qxe3 25.fxe3 Nxe2+ 26.Kf2 g4 27.Ng1 Nxg1 28.Rc1 Rxc1
  29.Bxc1 Bxg2 30.Kxg1 Bd5 31.Bd2 Bxa2 32.Bxb4 Kg6 33.Kf2 Kf5
  34.Bc3 h5 35.Kg3 Kg5 36.h4+ Kf5 37.Bd4 a5 38.Bc3 a4 39.Bd4 Ke4
  40.Kf2 1/2-1/2

.
  [FEN ""]
  [Event "1/4"]
  [Site "Cm  Las Palmas (06)"]
  [Date "1971.??.??"]
  [Round "6"]
  [Result "0-1"]
  [White "Wolfgang Uhlmann"]
  [Black "Bent Larsen"]
  [ECO "D47"]

  1.c4 Nf6 2.Nc3 e6 3.Nf3 d5 4.d4 c6 5.e3 Nbd7 6.Bd3 dxc4 7.Bxc4
  b5 8.Bd3 Bb7 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Nxc5 13.dxc5
  Bxc5 14.Bb5+ Ke7 15.O-O Qb6 16.Bd3 h6 17.Qe2 Rhd8 18.Bd2 Kf8
  19.Rac1 Rac8 20.Rc2 a5 21.Rfc1 Kg8 22.h3 Ne7 23.Ne1 Bd4
  24.Rxc8 Rxc8 25.Rxc8+ Nxc8 26.b3 Ne7 27.Nf3 Bc5 28.Be1 Nf5
  29.Kf1 Qc6 30.Bb5 Qc7 31.Bd3 Nd4 32.Nxd4 Bxd4 33.f4 Qc1 34.Qd2
  Qa1 35.Qc2 Bc3 36.Qb1 Ba6 0-1


2984: <p>Once when I was reading a book from Kasparov he quoted that most of the modern ideas in the semi-Slav came from Larsen games. Does anyone know good novelties that Larsen brings in this opening?   </p>
 1485: <p>Kasparov in <em>My Great Predecessors, Part 4</em>:</p>
<blockquote>
<p>Generally speaking, Larsen's contribution to the development of opening theory is not very great, since usually he aimed to lure his opponents into little-studied variations and mainly relied on his skill in the middlegame. Nevertheless, he played a key role in the development of what is currently one of the most popular lines in the Semi-Slav Defence, the so-called improved Meran Variation: <code>1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 e6 5 e3 Nbd7 6. Bd3 dc4 7.Bc4 b5 8.Bd3 Bb7!?</code></p>
</blockquote>
<p>One of Larsen's ideas was to allow a check on <code>b5</code> and give up castling rights. In return he got a strong knight on <code>d5</code>. He first used this idea in the Candidate match Ivkov-Larsen 1965, see game below. Read more about it <a href="http://www.chess.com/article/view/larsenrsquos-improved-meran-the-great-dane-deigns-to-allow-check" rel="nofollow noreferrer">here</a>.</p>
<p>Sample games:</p>
<pre><code>  [FEN &quot;&quot;]
  [Event &quot;Larsen-Ivkov Candidates Quarterfinal Match&quot;]
  [Site &quot;Bled YUG&quot;]
  [Date &quot;1965.07.05&quot;]
  [EventDate &quot;1965.06.27&quot;]
  [Round &quot;6&quot;]
  [Result &quot;1/2-1/2&quot;]
  [White &quot;Borislav Ivkov&quot;]
  [Black &quot;Bent Larsen&quot;]
  
  1.c4 Nf6 2.Nc3 e6 3.Nf3 d5 4.d4 c6 5.e3 Nbd7 6.Bd3 dxc4 7.Bxc4
  b5 8.Bd3 Bb7 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Bxc5 13.dxc5
  Nxc5 14.Bb5+ Kf8 15.Qd4 Qb6 16.Be2 h6 17.O-O g6 18.Bd2 Kg7
  19.Rac1 Rac8 20.Qh4 g5 21.Qg4 Ne4 22.Rxc8 Rxc8 23.Qxe4 Nf4
  24.Qe3 Qxe3 25.fxe3 Nxe2+ 26.Kf2 g4 27.Ng1 Nxg1 28.Rc1 Rxc1
  29.Bxc1 Bxg2 30.Kxg1 Bd5 31.Bd2 Bxa2 32.Bxb4 Kg6 33.Kf2 Kf5
  34.Bc3 h5 35.Kg3 Kg5 36.h4+ Kf5 37.Bd4 a5 38.Bc3 a4 39.Bd4 Ke4
  40.Kf2 1/2-1/2
</code></pre>
<p>.</p>
<pre><code>  [FEN &quot;&quot;]
  [Event &quot;1/4&quot;]
  [Site &quot;Cm  Las Palmas (06)&quot;]
  [Date &quot;1971.??.??&quot;]
  [Round &quot;6&quot;]
  [Result &quot;0-1&quot;]
  [White &quot;Wolfgang Uhlmann&quot;]
  [Black &quot;Bent Larsen&quot;]
  [ECO &quot;D47&quot;]

  1.c4 Nf6 2.Nc3 e6 3.Nf3 d5 4.d4 c6 5.e3 Nbd7 6.Bd3 dxc4 7.Bxc4
  b5 8.Bd3 Bb7 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Nxc5 13.dxc5
  Bxc5 14.Bb5+ Ke7 15.O-O Qb6 16.Bd3 h6 17.Qe2 Rhd8 18.Bd2 Kf8
  19.Rac1 Rac8 20.Rc2 a5 21.Rfc1 Kg8 22.h3 Ne7 23.Ne1 Bd4
  24.Rxc8 Rxc8 25.Rxc8+ Nxc8 26.b3 Ne7 27.Nf3 Bc5 28.Be1 Nf5
  29.Kf1 Qc6 30.Bb5 Qc7 31.Bd3 Nd4 32.Nxd4 Bxd4 33.f4 Qc1 34.Qd2
  Qa1 35.Qc2 Bc3 36.Qb1 Ba6 0-1
</code></pre>
