A quibble, but this comes up from time to time and it's not insignificant. The Marines in Beirut in '83 were armed and uniformed combatants in a war zone. A legitimate target.
Sure, we called them "peacekeepers" and they did originally enter the country to police a ceasefire. But the ceasefire collapsed, and the mission changed. The New Jersey, after all, was sitting offshore lobbing shells onto to bad guys ....
We clung to the fiction that the changed facts on the ground did not alter the Marines' status. That was a fatal mistake, as it led to security being lax. After all, no one was supposed to shoot at "peacekeepers."
Self-delusion is dangerous in war.