In War, what if one player runs out of cards mid-war?
Answers vary. From pagat.com:

Most descriptions of War are not clear about what happens if a player runs out of cards during a war. There are at least two possibilities:

If you don't have enough cards to complete the war, you lose. If neither player has enough cards, the one who runs out first loses. If both run out simultaneously, it's a draw. Example: Players A and B both play sevens, so there is a war. Each player plays a card face down, but this is player B's last card. Player A wins, since player B does not have enough cards to fight the war.

If you run out of cards during a war, your last card is turned face up and is used for all battles in that war. If this happens to both players in a war and their last cards are equal, the game is a draw. Example: Players A and B both play sevens, so there is a war. Player A plays a card face down, but player B has only one card, so it must be played face up. It is a queen. Player A plays a card face up and it is also a queen, so the war must continue. Player B's queen stays (B's last card) while player A plays a card face down and one face up, which is a nine. Player B wins the war and takes all these seven cards (the five cards that A played and the two cards that B played) and the game continues normally.