Snipers have historically been used by insurgents as a method of psychological warfare and attrition in Iraq, Syria, Yemen, Vietnam and Northern Ireland, including mobile units transported in vehicles. The highly urban areas of the Yemeni and Syrian civil wars and the Iraqi insurgencies and the rural areas of the Vietnam War and The Troubles provide ideal cover and positions for insurgent snipers, who kill or injure soldiers whenever possible and melt away to avoid enemy reinforcements and counterattacks.