The Blumenfeld Gambit with 1 d4 Nf6 2 c4 e6 3 Nf3 c5 4 d5 b5!? is a blood relative to the more universally popular Benko Gambit. While it was the invention of Russian master Benjamin Blumenfeld (1884-1947), it only became of interest after Alekhine used it to good effect as he destroyed Tarrasch in 1922 with a text-book advert for the gambit.
Modern master praxis has been to decline the gambit with 5 Bg5 rather than being faced with a strong pawn sacrifice for easy piece play and a direct attack a la Alekhine-Tarrasch. But in his latest Gambit Guide series for ICC, GM Boris Alterman shows that the Blumenfeld - even when White declines the gambit - has strategic depth beyond its first impressions