Chess Opening Theory/1. e4/1...c5/2. d4/2...cxd4/3. c3/3...dxc3/4. Nxc3/4...Nc6/5. Nf3/5...d6

Smith-Morra gambit accepted B21 Sicilian defence → Smith-Morra gambit → 5. Nf3 5...d6 Black adds control of e5. This also allows their queen's bishop to move off the back rank, though if Black is intending to develop their bishop in that direction they will have to play precisely. After 6. Bc4, Black isn't quite ready to develop their knight or bishop for tactical reasons. Black's main choices are to transposes into the Scheveningen structure with 6...e6, or prepare to develop their knight and bishop with the move 6...a6, leading to a classical structure. Theory table References