"If your opponent has an exposed king it is frequently worth sacrificing a pawn to be able to bring your rooks into the game, especially if your opponent's rooks are languishing in the corner. Kasparov has made a career out of such sacrifices."

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After a great deal of discussion in Soviet literature about the correct definition of a combination, it was decided that from the point of view of a methodical approach it was best to settle on this definition - A combination is a forced variation with a sacrifice.

— Alexander Kotov