Battle of Driniumor River The Battle of Driniumor River , also known as The Battle of Aitape , 10 July – 25 August 1944 , was part of the Western New Guinea campaign of World War II . Japanese forces attacked United States forces on the Driniumor River , near Aitape in New Guinea . The battle should not be confused with Operation Persecution , which included amphibious landing s near Aitape in April 1944 , or the Aitape - Wewak campaign , which began in November . The Japanese referred to the Driniumor as the " Hanto " . The river is approximately east of Aitape . The landings at several key points around Hollandia on 22 April had cut off the Japanese 18th Army , which was retreating westwards toward the Japanese Second Area Army in Dutch New Guinea . When U . S . troops landed and seized Aitape on 22 April , a covering force comprising the 32nd Infantry Division and 112th Cavalry Regiment was sent approximately 20 mi east to guard Aitape ' s eastern flank on the line of Driniumor River . The 18th Army — which had not been reinforced after severe losses in the Lae , Huon Peninsula and Finisterre Range campaign s — was commanded by Lieutenant - General Hatazō Adachi . Its main fighting units were the 20th and the 41st Divisions . Ultra intelligence derived from codebreaking as well as other sources indicated that the Japanese 18th Army was approaching the Driniumor with 20 , 000 troops with the intention of breaking through and retaking Aitape . Unfortunately , the Allied intelligence picture was confusing and contradictory , with the result that the initial Japanese assault caught the defenders by surprise . On the night of 10 / 11 July , an assault force of perhaps 10 , 000 Japanese attacked " en masse " across the Driniumor . Despite suffering appalling casualties from machine guns and artillery , the Japanese pressed on and forced a major breach in the American line . Ed Wanat a veteran of this battle stated that the Japanese bodies had piled up in front of their machine gun so high that they could not fire over them . They had to leave their fox holes and pull bodies out of the line of fire so that they had a clear line of fire upon the enemy . This occurred during the numerous Japanese attacks . After a harrowing fighting withdrawal through the jungle that night , the defenders managed to regroup where possible and by the 13th were counterattacking to try to seal the breach . Valuable fire support was provided by Australian and U . S . fighter bombers and by Task Force 74 ( TF 74 ) , comprising two Australian cruisers and two U . S . destroyers . The remainder of July saw heavy fighting west of the river as platoon and company size units clashed in the jungle . Heavy pressure was maintained upon some pockets of American troops still clinging to their positions at the river as they became encircled by Japanese troops , determined on wiping them out . By the beginning of August , however , the Japanese drive was spent and they were flung back over the Driniumor . By 4 August , Adachi ordered a complete withdrawal , although fighting lasted until around 10 August as U . S . troops continued their annihilation of the Japanese force . The remnants retreated further east to Wewak and the battle was officially declared over on 25 August . Four U . S . soldiers were awarded the Medal of Honor ( all posthumously ) , for acts of outstanding valor during the battle ; Private Donald R . Lobaugh and Staff Sergeant Gerald L . Endl of 32nd Division , and Second Lieutenants George W . G . Boyce , Jr . and Dale Eldon Christensen of 112th Cavalry Regiment . All told the Americans suffered almost 3 , 000 casualties including 440 killed while the Japanese lost 8 , 000 – 10 , 000 men . The four - week Battle of Driniumor River was one of the costliest of the campaigns in Papua and New Guinea , second only to the bloody head - on Allied assaults of the Japanese strongholds at Gona , Buna and Sanananda from November 1942 - January 1943 .