In 1965, US troops in Vietnam went from 25,000 to 184,000.
Comparing pre-1965 Vietnam casualties to Iraq casualties thus far is apples to oranges.
from Wikipedia's article on the
Vietnam War
Johnson raised the level of U.S. involvement on July 27, 1964 when 5,000 additional US military advisors were ordered to South Vietnam. This brought the total number of US forces in Vietnam to 21,000.
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On March 8, 1965, 3,500 United States Marines became the first American combat troops to land in South Vietnam, adding to the 25,000 US military advisers already in place. The air war escalated as well; on July 24, 1965, four F-4C Phantoms escorting a bombing raid at Kang Chi became the targets of antiaircraft missiles in the first such attack against American planes in the war. One plane was shot down and the other three sustained damage. Four days later Johnson announced another order that increased the number of US troops in Vietnam from 75,000 to 125,000. The day after that, July 29, the first 4,000 101st Airborne Division paratroopers arrived in Vietnam, landing at Cam Ranh Bay.
The Pentagon told President Johnson on November 27, 1965 that if planned major sweep operations needed to neutralize Viet Cong forces during the next year were to succeed, the number of American troops in Vietnam needed to be increased from 120,000 to 400,000. By the end of 1965, 184,000 US troops were in Vietnam. In February 1966 there was a meeting between the commander of the U.S. effort, head of the Military Assistance Command, Vietnam General William Westmoreland and Johnson in Honolulu. Westmoreland argued that the US presence had prevented a defeat but that more troops were needed to take the offensive, he claimed that an immediate increase could lead to the "cross-over point" in Vietcong and NVA casualties being reached in early 1967. Johnson authorized an increase in troop numbers to 429,000 by August 1966.