Slav Defence: Czech Variation
Also known as Czech Slav, Main-line Slav, Pure Slav
1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 dxc4 5.a4 Bf5
The classical main-line Slav. Black meets the Queen's Gambit with 2...c6, then after 4...dxc4 5.a4 develops the light-squared bishop to f5 before playing ...e6 – solving the Slav's eternal problem of the "bad" bishop by getting it outside the pawn chain first.
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What it does
It tackles the Slav's core challenge head-on. In many Queen's Gambit lines Black's c8-bishop ends up buried behind its own e6-pawn. Here Black first grabs the c4-pawn (knowing it cannot be held), forces White to spend a tempo on 5.a4, and then develops the bishop to f5 in the open air. Only afterwards does Black play ...e6 to support the centre. The result is harmonious, classical development with no bad pieces.
When to use it
Choose it when you want a rock-solid, principled defence to 1.d4 that keeps your pieces active rather than passive. It suits players who like clear strategic plans and sound structures over wild tactics. Because the theory runs deep and White has sharp tries (notably 6.Ne5 and the 6.e3 main lines), it rewards study – it is a main-line weapon favoured at the highest level, not a quick fix.
Why it works
The move 5.a4, while stopping Black from holding the pawn with ...b5, permanently weakens White's queen's side, especially the b4-square. Black gives the pawn back but gets a free, active light-squared bishop and easy development. The resulting positions are very sound: Black has no structural weaknesses, a fully developed army, and long-term targets on White's loosened queen's flank.
Key ideas
- Develop the c8-bishop to f5 before locking it in with ...e6.
- Take on c4, then give the pawn back – do not try to cling to it.
- White's a4 weakens b4 and the queen's side long term.
- Aim for harmonious, classical development with no bad pieces.
- Watch for White's sharp 6.Ne5, grabbing space and prepping f3 and e4.
- ...Bb4 pins the c3-knight and pressures the centre.
Watch out
Do not try to defend the c4-pawn with ...b5; after a4 it falls apart (axb5 cxb5 Nxb5) and Black's queen's side collapses – the pawn is meant to be returned. Also beware White's 6.Ne5, when f3 and e4 ideas can grab the centre and harass the f5-bishop; meet it accurately rather than drifting.