Estimates of casualties of the Vietnam War vary widely. Estimates include both civilian and military deaths in North and South Vietnam, Laos, and Cambodia. The war persisted from 1955 to 1975 and most of the fighting took place in South Vietnam; accordingly it suffered the most casualties. The war also spilled over into the neighboring countries of Cambodia and Laos which also endured casualties from aerial and ground fighting. Civilian deaths caused by both sides amounted to a significant percentage of total deaths. Civilian deaths were partly caused by assassinations, massacres, and terror tactics. Civilian deaths were also caused by mortar and artillery, extensive aerial bombing and the use of firepower in military operations conducted in heavily populated areas. A number of incidents occurred during the war in which civilians were deliberately targeted or killed. The most prominent of these events were the Huế Massacre and the Mỹ Lai Massacre. Total number of deaths Estimates of the total number of deaths in the Vietnam War vary widely. The wide disparity among the estimates cited below is partially explained by the different time periods of the Vietnam War covered by the studies and whether casualties in Cambodia and Laos were included in the estimates. A 1975 US Senate subcommittee estimated around 1.4 million civilian casualties in South Vietnam because of the war, including 415,000 deaths. An estimate by the Department of Defense after the war gave a figure of 1.2 million civilian casualties, including 195,000 deaths. According to statistics from the South Vietnamese Ministry of Health, 44.5% of civilians admitted to hospitals between 1967 and 1970 were wounded by mines or mortars, 21.2% by guns or grenades, and 34.3% by artillery or bombing. Guenter Lewy in 1978 estimated 1,353,000 total deaths in North and South Vietnam during the period 1965–1974 in which the U.S. was most engaged in the war. Lewy reduced the number of Viet Cong (VC) and People's Army of Vietnam (PAVN) battle deaths claimed by the U.S. by 30 percent (in accordance with the opinion of United States Department of Defense officials), and assumed that one third of the reported battle deaths of the PAVN/VC may have actually been civilians. He estimates that between 30 and 46% of the total war deaths were civilians. His estimate of total deaths is reflected in the table. A 1995 demographic study in Population and Development Review calculated 791,000–1,141,000 war-related Vietnamese deaths,