The Dog Who Stopped the War

During the winter break a large group of kids decide to break into two groups and play "war." One group stakes the kids barn/hideout as their base and the other group builds an amazing ice brick fortress complete with slides, a faux front door, and a snowball armory. The kids set up rules, spy on each other, get frustrated because they can't talk to kids on the other team. There is a conscientious objector, a kind of goofy nature-lovin' kid who tries to stop the war several times. I remember seeing this when I was pretty young and it made a lasting impression. I have only seen a dubbed into English copy (which makes some of the taunts the kids say pretty funny.)