After 4.Bxc6 bxc6 in the Rossolimo, both sides sign a long-term contract: Black takes the two bishops, White the healthier pawn structure. Which way the imbalance tilts then depends on a handful of small pawn decisions. In Middlegame Understanding – Rossolimo Structures – Part 1, GM Evgeny Romanov treats those structures as the real protagonists of the game — the frame inside which every plan either works or quietly fails.
