Johnson’s conflict seemed far less powerful in August of 1964, when, following the Gulf of Tonkin incident, American troops began pouring rapidly into Vietnam. Over the course of the war, over 3 million lives, including 58,000 Americans were lost. By 1973, President Richard Nixon withdrew troops from Vietnam, and in 1975 the communists marched into the South Vietnam capital of Saigon, officially marking the end of the resistance. The United States military failure in the war was due to a large number of factors, with a major one of them being the dense jungle terrain of Vietnam. It allowed the North Vietnamese Army (NVA) to attack by surprise and disappear just as quickly as they came. Along with many other considerations, including the tropical terrain, the service rifle of the USA has been investigated as a factor. The main service rifle, the M16 (or AR15), replaced the M14 as the primary service rifle for the army, which over time has garnered controversy for a wide variety of reasons.