both in theatre and at home , '' Smith said . Of the 4,000 U.S. military personnel killed in the war , 3,263 have been killed in attacks and fighting and 737 in non-hostile incidents , such as traffic accidents and suicides . Eight of the 4,000 killed were civilians working for the Pentagon . Many of those killed over the years , like the four soldiers slain on Sunday in Baghdad , have been targeted by improvised explosive devices -- the roadside bombs that have been described as the weapon of choice for insurgents and a weapon that has come to symbolize Iraq 's tenacious insurgency . The existence of the Pentagon 's Joint Improvised Explosive Device Defeat Organization has been developed to counter the threat of IEDs in Iraq as well as Afghanistan . The group calls IEDs the `` weapon of choice for adaptive and resilient networks of insurgents and terrorists . '' Watch how IEDs have become deadly staple in Iraq war '' Meanwhile , estimates of the Iraqi death toll range from about 80,000 to the hundreds of thousands , with another 2 million forced to leave the country and 2.5 million people displaced within
BAGHDAD , Iraq -LRB- CNN -RRB- -- Four U.S. soldiers died in a roadside bombing in Iraq on Sunday , military officials reported , bringing the American toll in the 5-year-old war to the grim milestone of 4,000 deaths . Troops emerge from a bunker after receiving the `` all clear '' Sunday following a truck bombing in Mosul . The four were killed when their vehicle was hit by an improvised explosive device while patrolling a neighborhood in southern Baghdad , the U.S. military headquarters in Iraq reported Sunday night . A fifth soldier was wounded in the attack , which took place about 10 p.m. -LRB- 3 p.m. ET -RRB- . The U.S. milestone comes just days after Americans marked the fifth anniversary of the start of the war . `` No casualty is more or less significant than another ; each soldier , Marine , airman and sailor is equally precious and their loss equally tragic , '' Rear Admiral Gregory Smith , the U.S. military 's chief spokesman in Iraq , said . `` Every single loss of a soldier , sailor , airman or Marine is keenly felt by military commanders , families and friends