Slav main line (4.Nc3 dxc4 5.a4) is variation 4 of 6 in the Queen's Gambit course, a intermediate opening course for White (ECO D17). It runs 26 moves and begins 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 dxc4 …. Black supports d5 with ...c6, then takes on c4 once White has committed the knight to c3. White stops ...b5 with a4, wins the pawn back with e3 and Bxc4, and aims for e4. In the lesson every move is explained on a board and then drilled; it is free.
Move by move
1. d4 – Takes the centre.
1... d5 – Black claims the centre.
2. c4 – The Queen's Gambit.
2... c6 – The Slav: defends d5 with a pawn and keeps the c8 bishop free.
3. Nf3 – Develops and controls e5.
3... Nf6 – Develops and defends d5.
4. Nc3 – Develops and presses d5 again.
4... dxc4 – Black takes the pawn now that the knight on c3 blocks the c-pawn's support.
5. a4 – Prevents ...b5, which would hold the extra pawn.
5... Bf5 – The bishop develops outside the pawn chain before ...e6.
6. e3 – Prepares Bxc4 to win the pawn back.
6... e6 – Opens the f8 bishop and supports d5 and f5.
7. Bxc4 – White wins the pawn back.
7... Bb4 – Pins the c3 knight and fights for e4.
8. O-O – White castles and unpins indirectly: the knight is no longer pinned to the king.
8... O-O – Black castles too.
The lesson goes on for 10 more moves, each with its explanation.
chessGM