Berlin Defense, Rosenthal Variation

5...a6 puts the question to the bishop so that Black can follow with ...d5, supporting the e4-knight once the c6-knight is no longer pinned. 6. Ba4 transposes to the Open Ruy Lopez, a move-order route that avoids sidelines such as the Wormald Attack. More common is 6. Bxc6 dxc6, an Exchange-like structure in which Nxe5 is a genuine threat. There, 7. Qe2 is preferred to regaining the pawn at once. The engine gives White a slight edge.