Looking for name of movie about kids fighting each other in a tree fort.

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Looking for name of movie about kids fighting each other in a tree fort.
I think the time period is post WWII, and I believe the movie was made in the 90's. It is about some kids that have a fort in the woods built in a huge tree and for some reason they start fighting with each other. One of the kids had a father who I think died in the war and his wife was given his hand gun wrapped up in the American flag. I believe that the uses the gun when they start fighting each other and I think a rocket launcher comes into their little skirmish at some point. I don't remember much more than this.
If anyone knows the name of the movie, please help me out.

Thank you for your time.