By 1966, the United States military faced a relentless adversary in the Mekong Delta: a water-logged terrain of endless canals, knee-deep silt, and flesh-rotting mud that rendered conventional tanks, trucks, and airfields useless. With the Viet Cong taxing the rice harvest and controlling the population from heavily fortified "secret zones," the U.S. Navy and Army executed an audacious plan. If they couldn’t base an army in the Delta, they would float one.

Enter the Mobile Riverine Force (MRF) a joint-service experiment pairing the Navy’s River Assault Flotilla 1 with the Army's 9th Infantry Division. Living aboard air-conditioned barracks ships and deploying in up-armored, rebar-draped landing craft known as "Tango" and "Monitor" boats, these sailors and soldiers crawled past the enemy's front door at a jogging pace, inviting fire to break ...