One of the last major underreported stories of the Vietnam War — a six-month campaign by U.S. troops that killed thousands of Vietnamese civilians — may now get the attention it deserves, thanks to a superb Dutch documentary that premiered in the Movies That Matter⁠ Festival in the Hague in March. The movie, called “Soldier’s Bones,” explores the military operation Speedy Express, carried out by the U.S. Army’s 9th Infantry Division in South Vietnam’s Mekong Delta from December 1968 to May 1969⁠. Speedy Express was intended to eliminate a Viet Cong stronghold in the Mekong Delta, but of the nearly 11,000 people killed whom the U.S. claimed were Viet Cong, it’s likely that 5,000 to 7,000⁠ were civilians, including thousands of women and children. Whatever the number, the operation was many times bloodier than the 1968 My Lai massacre, which killed nearly 500 villagers and is usually regarded as the most egregious commission of American war crimes in Vietnam. Even worse, while My Lai was a single action carried out by an Army captain and …