Essential viewing. This documentary about a group of American and Vietnamese war veterans, many of them disabled, bicycling 1,200 miles from Hanoi to Ho Chi Minh City is many things at onceact of witness, multicultural exchange, sports documentary, investigative journalism, and a mourning for the devastation of war. Ultimately it may be too many things to yield a cumulative effect, yet its scenes of former soldiers struggling with the meaning of the war are more moving than anything I’ve seen on the subject since Winter Soldier (a wartime agitprop film in which American veterans confessed their war crimes). The corporate sponsorship of the bicycle marathon adds many ironic layers, but the emotional encounters it permitted seem more important than anything else I’ve seen about our involvement in Vietnam. Coproduced by Chicago’s Kartemquin Films and directed by Jerry Blumenthal, Gordon Quinn, and Peter Gilbert (Hoop Dreams). 130 min. (JR)