This is an old chess variant for four players, probably originating from Russia, said to be played already in Russia around 1772. There has been a chess club in London in 1855, playing this variant, and Tchigorin, Capablanca, and Lenin (!) are said to have this game played.
The description here is mainly based on information from the book Zug um Zug: Die Zauberwelt der Brettspiele by Heinz Machatscheck; a book on games, made in communist East-Germany, but also on some information from Pritchard's book.
This game is played on a board of, in total 192 squares. There are in the corners of the board four fortresses, each of 16 squares. Each fortress has a gate, and pieces can only come into and out of the fortress through the gate.
The opening setup is as follows. However, note that players may deploy the pieces inside the fortress to their own choice, i.e., a usual set of pieces is placed in the normal way, and an additional rook, bishop, and knight are placed at will at the fortress at the right.
Players form two teams. Players at opposite sides are partners. Play continues clockwise.
Pieces move as in the normal chess game. However, as mentioned above, the fortress can only be entered or left when moving through the gate in the fortress. For this rule, the knight is assumed first to move straight, and then diagonally.
Pawns promote when they reach the last rank, either inside, or (more usual) outside a fortress.
There are two variants of this game. In the Russian variant, a player that is mated has his king removed, and his pieces are removed from the board. In the West-European variant, a player that is mated may not move. However, in this variant, when the mate is removed, then he can continue to play again. In both variants, the team that mates both opponents players wins the game.