According to the New Oxford American Dictionary:
It is a noun.
It is a war game in which blocks representing armies or other military units are moved about on maps.
Its origins can be traced to the late 19th century.
It is a combination of German words krieg “war” + spiel “game”
Special usage: A form of chess in which each player has a separate board and can only infer the position of the opponent’s forces fromm limited information given by an umpire who disallows illegal moves.
K.R.I.E.G.S.P.I.E.L 