故事发生是北爱独立战争期间。英国士兵乔迪（福里斯特·惠特克 Forest Whitaker 饰）在阿尔马遭到了北爱共和军的绑架，共和军企图用他来交换被英军扣押的俘虏。看守乔迪的是弗格斯（斯蒂芬·瑞 Stephen Rea 饰），他的内心对杀戮和战争感到迷失和无奈，对乔迪的遭遇感到恻隐与同情，他们成了好朋友。共和军最终没换来俘虏，上头要求弗格斯处决乔迪，弗格斯暗中放走了他。乔迪走前交给弗格斯一张他女朋友迪尔的照片，告诉弗格斯可以去伦敦找他的女朋友迪尔。
不料乔迪逃走时却误被来袭击的英军坦克轧死了，早已厌倦了战争的弗格斯逃到了伦敦，化名吉米。他在伦敦找到了迪尔，被她深深吸引，后来在旅馆时却发现她是男儿身。此时爱尔兰共和军传来消息，他们已经判了弗格斯死刑，他们要求弗格斯去执行一次同归于尽的任务！</p>...
Bang, bang, you're dead. No, really dead. A group of twelve year old kids play war in a forest but the audience views the action through their eyes. They fire real machine guns, hear mortars exploding around them, and dodge bloody shrapnel from grenades. I Declare War is a movie for young and adult audiences alike, featuring twelve to thirteen year old actors in the tradition of Stand By Me. With overtones of Lord of the Flies, I Declare War is a parable for not only events broadcast nightly on newscasts throughout the world, but a chilling depiction of the capacity for youth and man to take charge and to win at all costs....
