In mid-February 1944, the 37th Battalion, as part of 14th Brigade, was involved in the Battle of the Green Islands, codenamed Operation "Squarepeg". The aim was to secure an airfield for use in further advances in the Solomon Islands. On 15 February, the battalion was landed on the western side of Nissan Island, largely a coral reef, along with 35th Battalion. The 30th Battalion was landed on the eastern side of the island; collectively, the landings were the largest amphibious operation mounted by New Zealand forces in the war. Although the Japanese were present on the island, the landing was unopposed. Initially positioned to the north of the island's airstrip, it later moved to the village of Sior. Although the Japanese were reported to be in the south of the island, the battalion still carried out patrols to ensure none were still in their sector. Later in the month, soldiers from the battalion carried out landings on Sau, a small island to the northeast of Nissan Island, to deal with Japanese there. Four were wounded in exchanges of gunfire but this operation effectively ended any meaningful Japanese resistance in the area. With Nissan Island secure by 28 February, the battalion switched to a defensive mode of operations, monitoring for Japanese counterattacks and assisting in the building of the facilities necessary to allow the island to be used for air and sea operations.