What is White’s strongest move? There are two ways to see it: look for Black pieces on the same line, and spot the two rooks on the same dark-squared diagonal; or look for loose pieces, find the rook on d6, and experiment with attacks on it—especially along lines it shares with other enemy pieces. Either way the answer is straightforward: White plays Bb4, attacking both rooks. Black can move one of the rooks to protect the other, but he still loses the exchange.

This is an important pattern to remember. Anytime two enemy rooks are lined up on a diagonal, consider whether you might run them through with a bishop.