Black's supporting pawns resemble a mixture of the Orthodox Queen's Gambit Declined, e6, and the Slav Defense, c6.

About 80% of games continue 5.Bg5 or 5.e3: the former constitutes a sharp pawn sacrifice, while the latter restricts the dark-squared bishop from its natural development to g5.

Other possible moves are 5.Qb3, 5.g3 and 5.cxd5, the last of which, after 5...exd5, leads to a line of the QGD Exchange Variation where White's early Nf3 enables Black's queen bishop to freely develop, which should give equality (ECO codes D43 and D45).

This chapter looks at the first moves of the game from Black's point of view, assuming that he would prefer to play the Semi-Slav.

First, it allows Black to keep the option to enter the Slav Defense, i.e., developing his light-squared bishop to f5 at the appropriate moment, before moving his e-pawn.

Protecting the d5-pawn with the e-pawn allows Black to develop his kingside more rapidly, but it does block the light-squared bishop for the time being.

A typical line in the Noteboom Variation continues: 5.a4 Bb4 6.e3 b5 7.Bd2 a5 8.axb5 Bxc3 9.Bxc3 cxb5 10.b3 Bb7 11.bxc4 b4 12.Bb2 Nf6 13.Bd3 Nbd7 14.0-0 0-0 with an interesting position where Black has two connected passed pawns on the queenside, while White has the bishop pair and dominates the center of the board.

These opposing strategies, with the ensuing keen play, have long made the Meran a favorite for enterprising players of either color.

Black's main plan, on the other hand, is to find a way to push ...c6–c5 in order to free the long diagonal for his light-squared bishop and to eliminate the backward pawn on the semi-open c-file.

Pushing the e-pawn is the classical approach by White, adopted in several high-level games, including World Championship match Kramnik–Anand in 2008.

A third alternative is to play 11...Nxe5 (the Sozin Variation), and after 12.Nxe5 axb5 13.Bxb5+ Bd7 14.Nxd7 Qa5+ 15.Bd2 Qxb5 16.Nxf8 Kxf8 White probably has a slight advantage, but the imbalance in pawn structures will guarantee an exciting game with opportunities for both sides.

The strategic idea behind this move is to develop the light-squared bishop and possibly play b5–b4 and c6–c5 without wasting time on a7–a6.

The move 8...Bb7 was long considered virtually unplayable due to the line 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Nxc5 13.dxc5 Bxc5 14.Bb5+ and the black king will be stuck in the center.

The benefit of pushing the c-pawn is that should White play dxe6 and after the recapture fxe6 attack the e-pawn with either Ng5 or Nd4, Black has the opportunity to defend the pawn with ...Nc5.

An alternative approach is 15.Be3 h6, after which White can throw in the even flashier knight sacrifice 16.Nxe6, and the game typically continues 16...Nxe6 17.e5 Qxe5 18.Bg6+ (the point!)

Once a sideline, this move exploded in popularity in the 1990s, in large part due to Anatoly Karpov's advocacy.

A very radical approach by Black is to play 11...Rc8, with a clear threat of placing the rook on the same file as the white queen.

(12...a5 is the computer preference), and after 13.bxc5 Bxf3 14.cxd6 Nd5 the game is wide open with massive tactical complications and opportunities for both sides.

Popularized by Alexander Shabalov and Alexey Shirov, the gambit destabilizes the center for Black and has been successful for several grandmasters, including Kasparov, who won the first game of his 2003 match against the computer chess program Deep Junior with it.

White refuses to shut in the dark-squared bishop, instead developing it to an active square where it pins the black knight.

In some cases, such as the Cambridge Springs Defense (see below), Black aims to benefit from the slight dark square weaknesses left behind on the queenside after the bishop has moved outside the pawn chain.

Main Black replies are (in order of frequency in high-level games): 5...h6 (immediately questioning the white bishop's intentions, leading to Moscow/Anti-Moscow variations), 5...Nbd7 (transposing to the Cambridge Springs Defense), 5...dxc4 (triggering the ultra-sharp Botvinnik Variation) or 5...Be7 (transposing to the Orthodox Defense of the Queen's Gambit Declined).

All of this is combined with the fact that the Black king has no strong shelter to hide, so a constant threat of mating attacks hangs in the air.

The second one, first seen in 2008 in a game between Topalov and Kramnik, is the flashy 12.Nxf7 (a full piece sacrifice), which leads to a wild attack after 12...Kxf7 13.e5 Nd5 14.Ne4 Ke7 15.Nd6 Qb6 16.Bg4 and White has a great position, strong knight on d6, control over the center and the light squares, and pressure against the weak e6 pawn.

Although Black might be objectively able to survive and even convert his material advantage to a win, the complications are huge, and whoever is better prepared to deal with the position certainly has the upper hand in practical games.

The opening was introduced by Mikhail Botvinnik in the 1945 USSR vs. USA radio match vs. Arnold Denker.

Today, Alex Yermolinsky has an excellent record with the white pieces and Alexei Shirov has been Black's chief proponent in this variation.

Although this variation bears Botvinnik's name, he was not the first person known to have played it—Klaus Junge is credited as the actual inventor.

These positions are highly dynamic and favor first and foremost the better-prepared player, although objectively speaking White might have a slight advantage.

If Black continues with the typical 5...Nbd7, White can play 6.Bg5 and this is supposed to lead to a favorable version of a Queen's Gambit Declined.