The Second Battle of Fallujah took place as a result of the Iraq War. Since the Battle of Hu in 1968, it is regarded as the American troops’ most intense urban combat.
It is also regarded as the bloodiest American battle to have taken place during the fight and was fought solely against insurgents. The 1st Marine Division was ordered to reclaim Fallujah by American political authorities who understood that a major military reaction was necessary. 60 of the 200 renowned mosques in Fallujah were destroyed by coalition fire; several of these were weapon depots for the militants. The Americans suffered 95 overall casualties and 560 total wounds. There were an estimated 4,000 insurgents living there before the conflict; 2,000 of them are thought to have died, and another 1,200 are thought to have been taken.
Source:https://www.warhistoryonline.com/featured/second-battle-of-fallujah.html?safari=1
