En inglés.

What is the Hippopotamus system of defence? The idea is that, at the beginning of the game, Black develops within his own first three ranks. He constructs a solid, flexible and hopefully stable position, awaiting events. At the right moment, he will strike back! The Hippopotamus was given the name by an eccentric English amateur player JC Thompson, back in the 1950’s. It seems as good a name as any. Given the right conditions, Black will emerge from the chessboard swamp and crush all before them.