First Pacific tour, 1942-1943

After three months of shakedown, Mackinac, escorting a large convoy, departed the United States West Coast for Pearl Harbor, Hawaii, on 11 May 1942, arriving there on 19 May 1942. On 22 May 1942, the famous explorer Rear Admiral (retired) Richard E. Byrd and his staff came on board for an inspection cruise of U.S. bases in the South Pacific. Byrd, because of his worldwide recognition, had been drawn out of retirement to represent the United States to the French colonies in the South Pacific, which were nominally under the control of the pro-German Vichy government, as their cooperation was vital to the war effort there. Byrd debarked at Auckland, New Zealand, on 23 June 1942, and Mackinac then headed to Naval Base Noumea at Nouméa, New Caledonia, on 18 July 1942.

With preparations underway for the Guadalcanal‑Tulagi landing, scheduled for 7 August 1942 through 9 August 1942, Mackinac was assigned the task of setting up a seaplane base at Malaita, the most advanced post of the Guadalcanal campaign, while her PBY Catalina flying boats searched northward and westward to watch the sealane between Truk and Guadalcanal in case of any Imperial Japanese Navy reaction from its base at Truk. No American was known to have visited Malaita since Jack London in 1908, whence he had fled in disgust from fierce storms and head hunters. Now Commander Hitchcock took Mackinac up the back of the island and threaded his way into Maramasike Estuary on the southeast coast, through waters for which there were no charts. Mackinac opened for business with nine PBY Catalinas on the morning of 8 August 1942.^[1] One of the first American ships to anchor in the Solomon Islands, Mackinac retired to Espiritu Santo in the New Hebrides Islands on 12 August 1942.

Despite constant evacuation alerts and numerous search plane losses, Mackinac next set up base at Graciosa Harbor in the Santa Cruz Islands on 20 August 1942. Early on the morning of 12 September 1942, two Japanese submarines surfaced at the harbor entrance to shell Mackinac and the seaplane tender Ballard and their seaplanes. The two seaplane tenders returned fire, but neither side suffered damage.

Troop transport SS President Coolidge being abandoned after beaching.

Following her return to Espiritu Santo on 25 October 1942, Mackinac assisted with her boats in rescuing survivors of the United States Army transport SS President Coolidge after President Coolidge struck two naval mines in the harbor entrance and beached herself.

On 12 November 1942, Mackinac established an advanced seaplane base at Vanikolo Island in the Santa Cruz Islands, and began tending an average of six seaplanes a day. Several high-ranking officers visited her during this duty, including Vice Admiral William F. Halsey, Jr.

Mackinac got underway from Espiritu Santo with a convoy for the United States West Coast on 9 July 1943, arriving at San Francisco, California, on 25 July 1943. She then underwent a two-month overhaul at Mare Island Navy Yard at Vallejo, California.

Second Pacific tour, 1943-1945

Mackinac returned to Pearl Harbor on 28 September 1943. After a month of transport duty between Midway Atoll and Maui, Hawaii, Mackinac left Pearl Harbor on 20 November 1943 escorting the seaplane tender Curtiss to the Ellice Islands.

When a PBY Catalina flying boat was forced down near Nui in the Gilbert Islands, Mackinac, after locating it early on 24 November 1943, rescued the crew and safely towed the plane to Fenua Tapu despite adverse weather. On 1 December 1943 she arrived at recently secured Tarawa to tend seaplanes there through January 1944, undergoing 22 air raids during her time there.

Mackinac then steamed for Makin Atoll with Patrol Squadron 72 (VP‑72) to participate in the Marshall Islands campaign with around‑the‑clock seaplane tending. With Majuro Atoll and Kwajalein Atoll secured by the early part of February 1944, Mackinac was ordered on to Kwajalein Island, anchoring there on 9 March 1944. While her patrol bombing squadron was conducting rescue operations at Majuro, Makin, Eniwetok, and Kwajalein, Mackinac was laying out the seaplane area and assisting the construction of a naval airbase on Ebeye Kwajalein.

On 23 June 1944, Mackinac departed for Eniwetok en route to Saipan. As the American conquest of Saipan was still in the assault stage, Mackinac was under almost constant Japanese fire while stationed there.

Relieved at Saipan on 19 August 1944, Mackinac joined the seaplane tenders Chandeleur, Pocomoke, Yakutat, and Onslow in sailing for Kossol Passage, Peleliu, in the Palau Islands, arriving on 15 September 1944, one day after the American landings on Pelelieu. For the next three months, Mackinac marked navigational obstructions off Kossol before leaving for Ulithi Atoll on 25 December 1944. On 21 January 1945, Mackinac got underway with Chandeleur for San Diego, California, via Pearl Harbor, arriving at San Diego on 7 February 1945.

Third Pacific Tour 1945

Mackinac returned to Saipan in April 1945. On 11 May 1945, she joined a seaplane group based at Kerama Retto in the Ryukyu Islands during the Okinawa campaign, and continued a variety of duties, including air-sea rescue and bombardment of Japanese‑held Rose Island. After the seaplane group moved its operations to Okinawa on 14 July 1945, Mackinac tended motor torpedo boats through early August 1945. After the Japanese capitulation on 15 August 1945, she was assigned to join Task Group 30.5, arriving at Sagami Bay, Tokyo, Japan, on 28 August 1945.

Honors and awards

Mackinac received six battle stars for her World War Il service.