Blumenfeld gambit appears after the following moves 1.d4 Nf6 2.c4 e6 3.Nf3 c5 4.d5 b5!?. It happened many times that I used this variation in very important games, and succeeded. The player who does not this gambit may get smashed up. Black sacrifices a pawn but get the strong awn centre instead. The International Master Andrew Martin will familiarize you the Blumenfeld gambit.