4.Nbd2 O-O 5.a3 Be7: the bishop retreat is variation 5 of 6 in the Bogo-Indian Defence course, a intermediate opening course for Black (ECO E11). It runs 22 moves and begins 1. d4 Nf6 2. c4 e6 3. Nf3 Bb4+ 4. Nbd2 O-O …. White blocks with the knight and chases the bishop with a3. Black drops the bishop back to e7 and meets White's big centre with ...d6 and ...e5. After the trade on d4 Black gets free play. In the lesson every move is explained on a board and then drilled; it is free.
Move by move
1. d4 – White takes the centre.
1... Nf6 – Black develops and watches e4.
2. c4 – White gains space.
2... e6 – Black opens the f8 bishop.
3. Nf3 – White develops and avoids the pin on c3.
3... Bb4+ – The Bogo-Indian. Black develops with check.
4. Nbd2 – White blocks with the knight. Now a pawn on a3 can chase the bishop.
4... O-O – Black castles and waits.
5. a3 – White asks the bishop to decide.
5... Be7 – Black keeps the bishop. The d2 knight is not on its best square.
6. e4 – White builds a big centre.
6... d6 – Black keeps the centre closed for now and prepares e5.
7. Bd3 – White develops.
7... e5 – Black strikes at d4.
8. O-O – White castles.
8... exd4 – Black takes and opens lines for the pieces.
The lesson goes on for 6 more moves, each with its explanation.
chessGM