These were small affairs compared to the finale on Bougainville. With the withdrawal of the 3d Marine Division at the end of 1943, after it had successfully fought its way to the final defensive line, the two Army divisions, the 37th Infantry and the Americal, took over and extended the perimeter with only sporadic brushes with the Japanese.
Then, in late February and early March 1944, patrols began making “almost continuous” contact with the enemy. It appeared that the Japanese were concentrating for a serious counterattack. On 8 March, the 145th Infantry (of the 37th) was hit by artillery fire. Then the6th Division, parent of the old enemy, the23d Infantry, attacked hard. It took five days of “very severe” fighting, with support from a battalion of the 148th Infantry, combined with heavy artillery fire and air strikes, to drive the determined Japanese back. Meanwhile, the 129th Infantry had also been “heavily attacked.” The enemy kept coming and coming, and it was a full nine days before there was a lull on 17 March.
On 24 March the Japanese, after reorganizing, launched another series of assaults “with even greater pressure.” This time they also threw in three regiments of their17th Division. The artillery of both American divisions, guided by Cub spotter planes, fired “the heaviest support mission ever to be put down in the South Pacific Area.” That broke the back of the enemy attackers, and the battle finally was over on 25 March.
Major General Griswold, the corps commander, after eight major enemy attacks, wrote in a letter four days later:
I am absolutely convinced that nowhere on earth does there exist a more determined will and offensive spirit in the attack than that the Japs exhibited here. They come in hard, walking on their own dead, usually on a front not to exceed 100 yards. They try to effect a breakthrough which they exploit like water running from a hose. When stopped, they dig in like termites and fight to the death. They crawl up even the most insignificant fold in the ground like ants. And they use all their weapons with spirit and boldness.... Difficult terrain or physical difficulties have no meaning for them.
I am absolutely convinced that nowhere on earth does there exist a more determined will and offensive spirit in the attack than that the Japs exhibited here. They come in hard, walking on their own dead, usually on a front not to exceed 100 yards. They try to effect a breakthrough which they exploit like water running from a hose. When stopped, they dig in like termites and fight to the death. They crawl up even the most insignificant fold in the ground like ants. And they use all their weapons with spirit and boldness.... Difficult terrain or physical difficulties have no meaning for them.
The Americal Division had advanced along with the 37th in the March-April period with its last action 13–14 April. This ended the serious offensive action for the two Army divisions; the enemy had been driven well out of artillery range of the airstrips, 12,000 yards away.
For Americans this marked the end of the Bougainville saga: a tale of well-trained units, filled with, determined, skillful men, who fought their way to a resounding victory. The 3d Marine Division had led the way in securing a vital island base with the crucial isolation of Rabaul thus ensured.