During the period of rehabilitation following the Guadalcanal campaign, the 1st Marine Division received two new weapons—the M4 medium tank, nicknamed the Sherman in honor of William Tecumseh Sherman whose Union troops marched from Atlanta to the sea, and the M-1 rifle. The new rifle, designed by John C. Garand, a civilian employee of the Springfield Armory in Massachusetts, was a semi-automatic, gas-operated weapon, weighing 9.5 pounds and using an eight-round clip. Although less accurate at longer range than the former standard rifle, the M-1903, which snipers continued to use, the M-1 could lay down a deadly volume of fire at the comparatively short ranges typical of jungle warfare.

In addition, the division received the M4A1, an early version of the Sherman tank, which MacArthur valued so highly that he borrowed a company of them from the 1st Marine Division for the Hollandia operation. The model used by the Marines weighed 34 tons, mounted a 75mm gun, and had frontal armor some three inches thick. Although a more formidable weapon than the 16-ton light tank, with a 37mm gun, the medium tank had certain shortcomings. A high silhouette made it a comparatively easy target for Japanese gunners, who fortunately did not have a truly deadly antitank weapon, and narrow treads provided poor traction in the mud of New Britain.