Chess Opening Theory/1. d4/1...c5

1...c5 - Old Benoni Defence/ Benoni Defense
The Old Benoni Defense is quite rare and uncommon nowadays but can actually lead to a tactical and sharp game. Black takes a swipe with c5 and gambits a pawn for the exchange, develops, and gets pieces into the game. White normally responds with d5; taking the pawn is not recommended because of 2...e6, and if White tries defending, then a5 and White has no solutions to hold on to pawns while Black gains a tempo. This opening is quite rare nowadays. One idea for Black is to transpose to a Modern Benoni while avoiding the Four Pawn Attack (that is, variations with an early f2-f4 for White). Black can fianchetto his King's Bishop, and only after White plays Nf3 blocking an f-pawn, continue with ... e6 and ... exd5.

Another idea for Black is to keep the h8-a1 diagonal of Black's bishop open by delaying ... Nf6. Black could then play ... Ne7 instead of ... Nf6, or possibly, if White plays an early Nc3, give up his bishop by ... Bc3 to double the pawns.

Theory table
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1. d4 c5