La Diagonale du Figaro No. 42: the art of intuitive sacrifice in chess.
In his excellent manual, the great Austrian striker Rudolf Spielmann (1883-1942) was one of the first to classify the different ways of sacrificing. Tal, the magician of Riga, liked to say that in chess two plus two often equals five. For him, positional sensitivity, the direction of the attack took precedence over the precise calculation of variants. To succeed, a speculative sacrifice had to be guided.