Two Knights Defense, Polerio Defense, Bishop Check Line

The Bishop Check Line, 6. Bb5+, is White's most popular answer to the Polerio Defense. White does not retreat the bishop to e2 or b3 at once, and does not allow its exchange with 6. d3. Instead the check forces Black to interpose before the knight on a5 can capture anything, and it settles what happens to the pawn on d5.

Black usually blocks with 6...c6, chosen in about four games out of five. After 7. dxc6 bxc6 White's doubled d-pawns are gone and White keeps a sound extra pawn. Black gets the half-open b-file, faster development and the plan of ...h6 and ...e4 to chase the knight on g5. With the bishop attacked again, White chooses between 8. Be2, usually met by 8...h6, and 8. Qf3, which pins the c6-pawn. The alternative 6...Bd7 blocks with a piece, leaves Black's queenside pawns intact and offers a bishop trade. It scores marginally better for Black. 6...Nd7 is rarely seen. The engine rates the position as balanced, and draws are uncommon in online play.