Vietnam War changed U.S. policy on conflicts for generation

The Summer of '69 marked the beginning of a change in the way an increasingly battle-weary America would approach war.

During a July tour of Southeast Asian countries that year, President Richard Nixon announced that nations battling insurgents should no longer expect the United States to send troops.

The new president did so as Americans were being inundated by events that left them feeling the nation was more mired in Vietnam than ever. Coordinated Viet Cong attacks on Saigon and the countryside that February. The secret bombing of Cambodia that had begun that March. The eclipsing of America's Korean War death total that April. The bloody capture and subsequent abandonment of a single mountain - "Hamburger Hill" - which cost 72 U.S. dead and 372 wounded that May.

That June, Life magazine stunned the nation by printing the photographs of all 242 American troops killed during a single week.

Nixon's policy announcement ushered in a shift that, following America's humiliating 1973 troop withdrawal from Vietnam, kept America out of insurgent wars for a generation.

"America lost its stomach for what the Pentagon called low-intensity wars," said University of Kentucky Professor George C. Herring Jr., author of "America's Longest War: The United States and Vietnam, 1950-1975." "The [ U.S. military] was badly beaten up by the Vietnam War and came out determined not to fight that kind of war again."

By the early '70s, America's military leaders already had begun to reach toward conventional warfare, stressing heavy weapons such as the Abrams tank, and opening military training institutions designed to leverage America's technological advantages, including the Navy's "Top Gun" Fighter Weapons School.

In 1973, the Pentagon began assigning critical wartime responsibilities to National Guard and Reserve units, making it harder for a president to send troops into war without broad public support.

By the 1980s and early 1990s, American presidents had embraced schools of thought known as the Weinberger and Powell doctrines, which stressed avoiding war without overwhelming military power and clear, achievable goals.

"That didn't begin to erode until Bosnia and Kosovo in the 1990s," said Tom Hughes, a military historian at the Carl A. Spaatz Center for Officer Education in Alabama. "The invasion of Iraq and Afghanistan eroded it further."