Last month I taught M2 how to play War with some cards he had in his room. He has fun with it and he thinks it is funny when we are dramatic about it. ("You'll never take this queen!" or the excitement when a 3 beats a 2.)
It's really funny when we try to play when M3 is around. She runs over and grabs the cards as we set them down. Sometimes she hands them over and sometimes she keeps them.
It's like the wild militia attacking the trained formal troops.
M2 and I have our decks and we each play one card. The person with the higher card wins the battle and keeps the cards. M3 jumps on top of M2 and pulls until she comes away with some of his cards. Or she'll climb up on me and shout, throwing all my cards in the air.
If the point of the game is to collect the most cards, then her nontraditional approach is truly successful... but she does not seem concerned about escalation!