Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nc3/3...dxc4/4. e3/4...b5/5. Nxb5

Now leaving opening theory: This page represents a rare sideline. Before making new pages for following moves, please consider line notability.

This clever attempt to win material is a huge mistake, providing Black with a huge advantage.

Black should undoubtedly continue with 5...cxb5, taking the offered piece. Now 6. Qf3 is White's only way to try to capitalise on their sacrifice, threatening to take the rook on a8. Black does have a few ways out.

6...Qc7 is the most principled. Black will try to trap the white queen if the rook is taken. White should continue with their plan, since backing out now would leave Black up a clean piece. 7. Qxa8 Bb7 8. Qxa7 e5! White's queen is trapped and 9...Nc6 is threatened. White has to give up another piece to save the queen: 9. Bxc4 bxc4 and the queen can escape to a4. White ends up with two pawns and a rook for two pieces, but White is also severely behind in development.

Alternatively, 6...Nc6 can be played, giving back the piece but gaining a ton of initiative: 7. Qxc6+ Bd7 8. Qa6 e5!. Material is equal, but Black has way more active pieces and a queenside space advantage.

6...Na6 is another interesting idea, temporarily giving up the rook for a vicious attack on White. The idea is 7. Qxa8 Nb4, threatening to fork the white king and rook. White's king can't go on the light squares, since that would allow a check with Black's light-squared bishop, revealing an attack on the white queen. While equal according to computer analysis, the position requires Black to play very accurately if they wish to keep their advantage.

1. d4 d5 2. c4 c6 3. Nc3 dxc4 4. e3 b5 5. Nxb5

Wikipedia has related information at Slav Defence.