The First Battalion of the 24th Infantry Regiment, with Lee, was soon reassigned to Bougainville Island, where it was attached to the 37th Infantry Division. Here, in the Bougainville Campaign, the 37th Infantry Division fought against the Japanese 3rd Battalion, 23rd Infantry, 13th Infantry, and 6th Division. The Bougainville Campaign, in the Solomon Islands, was last campaign of the American military effort to open up a direct route to the Philippines through the Solomon Islands. The Japanese had placed 25,000 stationed troops on Bougainville by this time. Due to the difficult heavy jungle terrain of the island, the 37th Infantry Division, paired with the 3rd Marine Division took an offensive-defensive approach to the campaign. During this time, Lee, along with the 24th Infantry Regiment, saw directly fought the Japanese in a two month-long battle of attrition. On March 8, 1944, the Japanese commenced a massive attack on the Americans, during which the Americans suffered many casualties. The attack ended on March 13, 1944, with the defeat of the Japanese. Nevertheless, fighting continued. It was in this subsequent fighting that, on March 16, 1944 (interestingly, two days after his divorce), Jerry was killed in the Bougainville Campaign.
Lee was buried on the day after his death in a cemetery on Bougainville island. Lee was reinterred to the US Air Force Cemetery in New Guinea on March 13, 1945. Jerry was finally transferred to and buried in Block A, Row 15, Grave 29 of the Manila American Cemetery in Taguig City in the Philippines, the Manila American Cemetery is the largest cemetery for American World War II soldiers, with 17,184 buried.