Originally published in 1984, this a volume in the Combat Studies Institute "Leavenworth Papers" series. On the night of 10-11 July, several thousand Japanese infantrymen attack and broke through U.S. Army covering force units defending the Driniumor River about twenty miles east of Aitape, New Guinea. For the next month U.S. army troops were locked in a battle of attrition with the Japanese, as the Americans fought to restore the breakthrough line and destroy the Japanese attackers. This study describes the events leading up to the Japanese breakthrough and the subsequent American counterattack to restore the original defensive positions. Include photos. maps, tables.