The US ships made radar contact with the Japanese force at 23:33. Moosbrugger's battle plan divided his forces into two divisions. Moosbrugger's own Destroyer Division 12 ("Dunlap", "Craven" and "Maury"), whose ships retained their full pre-war torpedo batteries, was to launch a surprise torpedo attack out of the shadow of Kolambangara Island. Meanwhile, Commander Roger Simpson's Destroyer Division 15 ("Lang", "Sterett" and "Stack"), whose ships had exchanged some of their torpedo tubes for extra 40 mm guns, was to cover Moosburger's division from an overwatch position, turning to cross the enemy's course. The idea was that any attempt by the Japanese to turn into the first division's torpedo attack would expose their broadsides to torpedo attack from the second division.