Multinational War is Hard
arXiv:1503.00141
Abstract
In this paper, we show that the problem of determining whether one player can force a win in a multiplayer version of the children's card game War is PSPACE-hard. The same reduction shows that a related problem, asking whether a player can survive k rounds, is PSPACE-complete when k is polynomial in the size of the input.
10 pages [fixed references]