Forces have trained. 1973, the last u.s. combat soldiers leave in march. the war is over. but the north vietnamese me keep fighting until saigon falls. at 4:03 a.m. april 30th, 1975, two u.s. marines corporal charles mcmahon and lance corporal darwin judge are killed at the saigon airport. they were the last u.s. troops, trace, to die in vietnam. america's longest war, trace? >> jennifer griffin live for us in washington. jennifer, thank you. well, a child is presumed dead after a family's holiday on the water ended with frantic search. rescue crews say a small boat sank this morning in the co...