The Dog Who Stopped the War (1984) trailer

As the Christmas holidays begin, a group of 10 war-obsessed kids have a wave of inspiration: What if they spend the next two weeks engaged in a simulated war, armed only with shields, wooden swords, snowballs, and a fierce sense of competition? With a bounty chest waiting for the winners, the two sides gradually grow in size, and the war grows in importance, taking over all aspects of their lives. But the sense of fun and excitement soon turns to something far darker, culminating in a tragic event that ensures this war will never be forgotten.