Classical Defense

With 5...c5 Black finishes the ...e6 setup by attacking d4 before White has completed development. The c- and d-files are half-open, and the central tension usually resolves with ...cxd4. An exd4 recapture leaves White an isolated queen's pawn, while a piece recapture gives a more symmetrical structure. White castles with 6. O-O, the Normal Line, in roughly seven games out of ten. 6. Nc3 is the main alternative and 6. dxc5 is rare. The Furman Variation, 6. Qe2, backs up the e-pawn's advance and allows dxc5 without trading queens.

After 6. O-O, the Main Line 6...a6 prepares ...b5 to gain time on the bishop. White can allow it with 7. Qe2, the Alekhine System, or rule it out with 7. a4, the Rubinstein Variation. The sharper 7. e4, known as the Russian Gambit, is usually reached through a 3. e3 move order. The Steinitz lines branch off a move earlier: 6...Nc6 is the Development Variation, and 6...cxd4 releases the tension at once in the Exchange Variation. The engine sees the position as roughly balanced, and results on Lichess are almost exactly even.