Members of the 9th U.S. Marine Expeditionary Force go ashore at Danang, South Vietnam, on March 8, 1965. Assigned to beef up defense of an air base, they were the first U.S. combat troops deployed in the Vietnam War. AP hide caption

itoggle caption AP

Vietnamese forces travel toward the country's northern border during a brief, bloody war with China in 1979. Alan Dawson/Bettmann/CORBIS hide caption

itoggle caption Alan Dawson/Bettmann/CORBIS

Brig. Gen. Viet Luong of the 1st Cavalry Division came to the United States in the 1970s after his family fled Vietnam in the waning days of the war there. He's now leading the effort to train Afghan soldiers to fight the Taliban. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Jan Scruggs gazes up at the names of fellow military service members inscribed on the Vietnam Veterans Memorial in Washington, D.C. Steve Inskeep/NPR hide caption

itoggle caption Steve Inskeep/NPR

A U.S. Air Force C-123 sprays herbicides on dense jungle beside a South Vietnamese highway on May 18, 1966. This aircraft is the last in a formation of three. Spray from the other two planes can be seen ahead. U.S. Air Force via AP hide caption

itoggle caption U.S. Air Force via AP

After a photo of Lanny Martinson's dog tag was placed on Facebook and elsewhere, Marines and veterans helped track him down. Martinson lost the tag in Vietnam in 1968. Facebook hide caption

itoggle caption Facebook

Democratic presidential candidate George McGovern talks about the bombs being used in Vietnam at a $250-a-person fundraising dinner in Los Angeles on Sept. 27, 1972. AP hide caption

itoggle caption AP

July 1, 1971: After getting the green light from the Supreme Court, The New York Times resumes publication of its series of articles based on the secret Pentagon Papers. Jim Wells/AP hide caption

itoggle caption Jim Wells/AP