French Defense, Classical, 4. Bg5 is a chess opening with the ECO code C12. It goes 1. e4 e6 2. d4 d5 3. Nc3 Nf6 4. Bg5. White opens with 1. e4 (the king's pawn) and Black answers 1... e6. After 7 moves it is Black to move. The lesson on the board explains every move of the line and lets you play it yourself; it is free.
The moves
1. e4 – White plays the pawn to e4
1... e6 – Black plays the pawn to e6
2. d4 – White plays the pawn to d4
2... d5 – Black plays the pawn to d5
3. Nc3 – White plays the knight to c3
3... Nf6 – Black plays the knight to f6
4. Bg5 – White plays the bishop to g5
In chessGM's opening book this position continues with 4... Be7.
About the French Defense, Classical, 4. Bg5
Black answers 1.e4 with 1...e6 and then ...d5, attacking White's centre. Black accepts a little less space for a very solid position.
If White plays e5, pawn chains form: White attacks on the kingside, Black on the queenside.
Black hits the chain at its base with ...c5 and adds pressure with ...Nc6 and ...Qb6.
The light-squared bishop on c8 is often passive; Black may trade it or free it with ...b6 and ...Ba6.
chessGM