Gilliam was part of a 36-ship convoy churning toward the Philippines when, on 5 December 1944, the convoy came under heavy air attack while from Leyte Gulf. At 12:18 Gilliam spotted a plane coming in low on the water at deck level, headed for the middle of the convoy. Coming under limited fire, the Japanese plane released a torpedo two minutes later which smashed into. Just after 12:30 two more planes came in low and fast, and one got another torpedo into the stricken merchantman, which was then dead in the water. Intense fire from the convoy drove the planes off, but later that afternoon another Japanese aircraft dove in at 15:30, and after running into heavy fire, made a suicide crash on SS Marcus Daly. The Japanese caught her on the bow at waterline and started fires and explosions. A second kamikaze tried his luck but missed and crashed into the sea after repeated hits from the convoy's gunners. Anton Saugraine and Marcus Daly were kept afloat by quick damage control, but the former ship was attacked again the next day while under tow and finally sunk. During this engagement, Gilliam's unflinching crew stood at General Quarters for nearly 12 hours and the ship reached Leyte 6 December without damage.
Invasion of Luzon
At Leyte Gilliam acted as receiving ship for the crews of damaged warships and undertook medical and salvage operations in spite of continued air alerts. After embarking over 500 soldiers at Tacloban, she sailed from that port 7 January 1945 bringing troops to Lingayen Gulf in support of the invasion. She returned to Leyte on 14 January to embark elements of the 32nd Infantry Division and brought them safely back to Lingayen Gulf 27 January.
After loading casualties for passage to Leyte, Gilliam sailed from that port 2 February to embark Marines of the III Amphibious Corps at Guadalcanal and conducted training exercises in preparation for the coming invasion of Okinawa. Gilliam closed Okinawa on 1 April and in the face of kamikaze attacks debarked reconnaissance parties of the 3d Amphibious Corps and unloaded vital cargo. On 5 April she sailed for the United States via Saipan and Pearl Harbor, mooring at San Francisco 27 April for drydock repairs. Subsequently Gilliam embarked men of the 6th Seabee Battalion a Port Hueneme, California, and sailed 28 May 1945 for Okinawa via Eniwetok and Ulithi. She off-loaded cargo and passengers at Okinawa and then headed back to San Francisco.
After hostilities
Gilliam arrived back at San Francisco on 10 August, where nearly 1,000 troops were embarked and brought to Pearl Harbor on 27 August. Men of the Headquarters and Service Battalions, 5th Amphibious Corps came on board at Hawaii, and Gilliam sailed 1 September for Sasebo, Japan, and put her occupation troops ashore 3 weeks later. On 25 September 1945 she got underway for Manila, and after embarking more than 450 veterans of the 33rd Infantry Division at Lingayen Gulf, she carried them to Sasebo, arriving 15 October.
After returning to Cebu in the Philippines 29 October, she became part of the Operation Magic Carpet fleet and sailed 2 November with 1,000 sailors and soldiers, debarking them at Portland, Oregon, 21 November 1945.
Operation Crossroads
Following a voyage to Samar, Gilliam moored at Pearl Harbor on 16 February 1946 and prepared to participate in the atomic bomb tests at Bikini atollin the summer of 1946. On the morning of 1 July 1946, Gilliam, a target ship for Test Able, was the first ship struck by the blast and sunk in Bikini lagoon. She was decommissioned, 5 July 1946 and struck from the Naval Register, 20 July 1946
Decorations
Gilliam received three battle stars for World War II service and two Navy Occupation Service Medals for her actions during the occupation of Japan.
