War takes place between sovereign states (the Russo-Japanese War, the war between India and Pakistan that led to the creation of Bangladesh, the Iran-Iraq war are all examples). Most modern armed conflicts are not like that - they are conflicts between a state and guerillas supported by some ethnic, religious or social group. The conflicts in Chechnya, Kurdistan, Kashmir, Kosovo, Palestine and many more are or were like that. Informally, they are referred to as wars, even though formally nobody declares war at the beginning or capitulates at the end (for example, formally the United States never fought the Vietnam War, because who would it declare war against - the Viet Cong?). Anyway, Rachel Corrie and her confreres came to a war zone and decided to get involved in the war - they should have expected that some of them would die.