Slav and Semi-Slav Defense

Once White has committed the knights, Black grabs the c4 pawn. Unlike the Queen's Gambit Accepted, the c6 pawn now supports ...b5, so White cannot simply win it back with e3 and Bxc4. White has to spend a move on a4 or play the gambit 5.e4 b5.

5.a4 stops ...b5, but it leaves a permanent hole on b4 for Black's bishop and knight. 5...Bf5 develops the bishop outside the pawn chain and stops e2-e4 for the moment. White will win the c4 pawn back; Black will have a harmonious setup and a solid outpost.

With the light bishop outside, ...e6 no longer costs anything. The f8 bishop goes to b4, using the hole a4 created and pinning the c3 knight so that White's e3-e4 is harder to achieve. This is the classical main line of the Slav.

In the Semi-Slav Black accepts a blocked c8 bishop for now and waits until White has spent a move on Bd3. Then ...dxc4 and ...b5 gain time on the bishop and grab queenside space: this is the Meran, named after the 1924 Merano tournament where Ernst Grünfeld used it with success. The bishop will come to b7 and the freeing ...c5 follows.

The Slav structure is solid but a little passive, and Black frees it with one of two pawn breaks: ...c5 (opening the long diagonal for the b7 bishop) or ...e5 (once the pieces cover e5). Timing is everything: played too early, the break drops a pawn or walks into a fork; played at the right moment, Black equalises completely.

In the Semi-Slav Black's dark bishop often stands on d6, next to the knight on f6. It is a good square, but it is exposed: e4-e5 can fork it with the f6 knight, c4-c5 can hit it, and a white bishop on f4 or g3 can offer a trade that exposes it. Most of the tactics in this opening start with that bishop.

White's main plan is e3-e4 (prepared by Qe2 or Nh4) to gain the centre with tempo on the f5 bishop, then e4-e5 to push the f6 knight away and use the e4 and e5 squares. Black keeps the bishop safe on g6 or h5 and answers with ...Nd5, ...c5 or ...e5 depending on where White's pieces go.

Black uses b4 as an outpost and pins the c3 knight to slow down e4. When White trades the light bishop with Ne5 and Nxg6, Black recaptures towards the centre with the h-pawn and gets an open h-file and a very solid king. The plan is ...Qa5 or ...Qe7, then ...e5 or ...c5 to free the position.

Black's pawns on a6 and b5 give space and a later ...b4 kicks the c3 knight; ...c5 opens the long diagonal for the b7 bishop and challenges White's centre. White's answers are e4-e5 or d4-d5 to open lines before Black is fully developed, which makes the Meran one of the sharpest parts of the Semi-Slav.

Against an early ...Bf5 White can chase the bishop and trade it off with Nh4xg6. White gets the bishop pair and a small, long-term edge; Black gets the half-open h-file and a compact position, and plays for ...Bd6, ...Qe7 and a later ...e5.

In the symmetrical structure there are no pawn breaks to speak of, so the game is decided by piece activity: whoever controls the open c-file and the entry squares c7 (for White) or c2 (for Black) is better. Black's ...a6 takes b5 away from White's knight, the most common source of Nc7+ tricks.