Following post-commissioning fitting out at the Philadelphia Navy Yard, Alaska stood down the Delaware River on 6 August 1944, bound for Hampton Roads, escorted by Simpson and Broome. She then conducted an intensive shakedown, first in Chesapeake Bay and then in the Gulf of Paria, off Trinidad, British West Indies, escorted by Bainbridge and Decatur. Steaming via Annapolis, Maryland, and Norfolk, Alaska returned to the Philadelphia Navy Yard, where the large cruiser underwent changes and alterations to her fire control suite: the fitting of four Mk. 57 directors for her five-inch battery.
Alaska departed Philadelphia on 12 November 1944 for the Caribbean, in company with Thomas E. Fraser, and, after two weeks of standardization trials out of Guantanamo Bay, Cuba, sailed for the Pacific on 2 December. She completed her transit of the Panama Canal on 4 December, and reached San Diego on the 12th. Thereafter, the new large cruiser trained in shore bombardment and anti-aircraft firing off San Diego before an availability at Hunter's Point, near San Francisco.
Alaska sailed for the Japanese home islands as part of TG 58.5 on 10 February 1945, assigned the mission of screening the aircraft carriers Saratoga and Enterprise as they carried out night air strikes against Tokyo and its airfields. During the voyage, all hands on board Alaska speculated about what lay ahead — almost three-quarters of the men had never seen action before and sought out the veterans in their midst "for counsel and advice." Sensing the air of expectation on board his ship, Captain Noble spoke to the crew over the public address system and reassured them of his confidence in them. In doing so, he used an analogy familiar to most Americans: "We are a member of a large task force which is going to pitch directly over the home plate of the enemy," he said, "It is our particular job to back up the pitchers."
With the decision reached to occupy Okinawa, in the Nansei Shoto chain, in early April 1945, invasion planners proceeded on the assumption that the Japanese would resist with maximum available naval and air strength. To destroy as many aircraft as possible-and thus diminish the possibility of American naval forces coming under air attack from Japanese aircraft-the fast carrier task force was hurled against the enemy's homeland again: to strike airfields on Kyūshū, Shikoku, and western Honshū. Alaska, still with TG 58.4-formed around the fleet carriers Yorktown, Intrepid, Independence and Langley again drew the duty of protecting the valuable flattops. Her principal mission then, as it had been before, was defense of the task group against enemy air or surface attacks.
Its battle plan outlined in detail, TF 58 cruised north-westerly from the Carolines, following the departure from Ulithi on 14 March. Refueling at sea on the 16th, this mighty force reached a point southeast of Kyūshū early on the 18th. On that day, the aircraft from TG 58.4 swept over Japanese airfields at Usa, Ōita, and Saeki, joining those from three other task groups, TG 58.1, TG 58.2, and TG 58.3 in claiming 107 enemy aircraft destroyed on the ground and a further 77 (of 142 engaged) over the target area.
Soon thereafter, Alaska received word of the proximity of "friendlies" in the vicinity. At 08:22, a single-engine aircraft approached the large cruiser "in a threatening fashion" from ahead, in a shallow dive. Alaska opened fire promptly and scored hits. Unfortunately, almost simultaneously her fire controllers were receiving word that the aircraft was, indeed, a friendly F6F Hellcat. Fortunately, the pilot was uninjured and ditched his crippled aircraft; another ship in the disposition picked him up.
For the balance of the day, the suicide attacks continued. The vigilant combat air patrol (CAP), however, downed a dozen aircraft over the task force while ships' gunfire accounted for almost two dozen more. Alaska added a second enemy bomber to her "bag" when she splashed a Yokosuka D4Y "Judy" at about 13:15.
The next morning, the 19th, photo reconnaissance having disclosed the presence of a large number of major Japanese fleet units in the Seto Inland Sea, TF 58 launched aircraft to go after them. TG 58.4's aircraft took on targets of opportunity at Kobe; others at Kure and Hiroshima. Extremely heavy and accurate enemy antiaircraft fire, however, rendered the attacks only moderately successful for TF 58's aviators.
The thin cloud layer having rendered radar largely useless, Japanese aircraft attacked all task groups. During the afternoon, TF 58 retired slowly to the south-westward, covering the crippled Franklin and simultaneously launching fighter sweeps against airfields on Kyūshū in order to disorganize any attempted strikes against it. To further protect Franklin, a salvage unit, Task Unit (TU) 58.2.9, was formed.
Composed of Alaska, her sister ship Guam, the heavy cruiser Pittsburgh, the light cruiser Santa Fe, and three destroyer divisions, TU 58.2.9 drew the duty of screening the damaged "Big Ben," as Franklin had been affectionately nicknamed by her crew. Ordered to make its best speed toward Guam, TU 58.2.9 set out in that direction, covered by TU 58.2.0, four aircraft carriers and the remaining heavy units originally assigned to TG 58.2 at the outset.
The initial part of the voyage proved uneventful, and not until the afternoon did Japanese aircraft appear. Several bogies (unidentified aircraft) showed up on the radar screens; investigation revealed most to be Navy PB4Y patrol bombers failing to show IFF (identification, friend or foe). Two of three CAP divisions sent out to challenge a bogey identified it as a PB4Y; unfortunately, because the friendly character of one bogey was established, the interception of a second bogey at about the same time failed to materialize. Only poor marksmanship on the part of the "Judy" pilot saved Franklin from another bomb hit. Alaska added to the hail of gunfire put up on the "Judy" but it sped away, unscathed. The final salvo from Alaska's mount 51 caused flash burns on the crew of a 40 mm mount nearby—the only casualties suffered by the large cruiser. Later that day, Alaska received on board 15 men from Franklin for medical treatment.
The following morning, Alaska assumed fighter director duty, and controlled three divisions of fighters from Hancock. While these divisions remained on station pending the arrival of their relief, Alaska's SK radar picked up a bogey, 35 miles (56 km) away, at 11:43. The large cruiser vectored the CAP fighters to the scene, and at 11:48, heard the "tallyho" indicating that the CAP had spotted the bogey. At 11:49, the fighters splashed a Kawasaki Ki-45 "Nick" 19 miles (31 km) away.
On 22 March, Alaska's part in the escort of the damaged Franklin was complete, and she rejoined TG 58.4, fueling that same day from Chicopee. At 23:42, one of the destroyers in the screen, Haggard, reported a "skunk" (submarine contact) 25,000 yards distant. She and Uhlmann were detached to investigate, and early the next morning, Haggard rammed and sank a Japanese submarine (perhaps I-370, which had departed the Bungo Channel on 21 February 1945 for Iwo Jima as part of a special kaiten-carrying attack unit), suffering enough damage herself in the encounter to be ordered back to base in company with Uhlmann.
Ordered to carry out the shoot en route to a fueling area, Alaska and Guam and their screen steamed west of the island on north/south courses between 22:45 on 27 March and 00:30 on the 28th. Alaskas main battery hurled 45 high-capacity rounds shoreward, while her five-inch battery added 352 rounds of antiaircraft common. No answering fire came from the beach, and Alaskas observers noted "satisfactory fires" on the island.
Rejoining TG 58.4 at the fueling rendezvous, Alaska transferred the Franklin wounded to the oiler Tomahawk while she took on fuel. She then resumed her screening of the fast carriers as they carried out operations in support of the build-up and landing on Okinawa, on the alert to repel aircraft attacks. The landings went off as scheduled on 1 April, and her operations over ensuing days supported the troops. On 7 April, Japanese surface units moving through the East China Sea toward Okinawa to disrupt the landings ran afoul of a massive air strike from Vice Admiral Marc Mitscher's fast carrier task force which sank the giant battleship Yamato, one cruiser and four destroyers.
Operating off Okinawa and Kyūshū, Alaska lent the protection of her guns to the fast carriers in the task group which sent daily sweeps of "Hellcats" and "Corsairs" over enemy airfields, shore installations and shipping. On the evening of 11 April, Alaska chalked up an assist in shooting down a Japanese aircraft, shot down one, unassisted, and claimed what might have been a piloted rocket bomb "Baka" on the night of 11–12 April.
Four days later, on the 16th, Alaskas gunfire splashed what were probably a "Judy" and two "Zekes," and the ship claimed assists in downing three additional enemy aircraft. That same day, however, an enemy aircraft managed to get through Alaskas barrage to crash into Intrepid. That night, though, the cruiser's gunfire proved instrumental in driving off a single snooper attempting to close the formation. On the night of 21–22 April, the cruiser again used her heavy antiaircraft battery to drive off single aircraft attempting to attack the task group. On the night of 29–30 April, toward the end of the ship's time at sea with the fast carriers for that stretch, Alaska twice drove off attacking groups of Japanese aircraft.
Subsequently, the task group sailed south-westerly for San Pedro Bay, Leyte, reaching its destination on the afternoon of 13 June 1945. A month in Leyte Gulf then ensued—a period of "rest, refreshment, and maintenance"—before Alaska sailed again on 13 July, this time as part of the newly formed TF 95. Reaching Buckner Bay, Okinawa, on the 16th, TF 95 fueled there and then sailed the following day, bound for the coast of China and a foray into the East China Sea, long a hunting ground for American aircraft and submarines but not entered by an American surface force since before Pearl Harbor.
Although planners for the sweep had anticipated resistance, none materialized; Alaska, Guam, and their escorts ranged the area at will, encountering only Chinese fishing junks. Enemy aircraft venturing out to attack the task force several times fell to CAP fighters. Operating out of Buckner Bay, Alaska participated in three sweeps into these waters, and all could see how effective the blockade of Japan had become; no Japanese ships were sighted during the course of the operation. Commented Guam's commanding officer, Captain Leland P. Lovette: "We went prepared to tangle with a hornet's nest and wound up in a field of pansies—but we've proved a point and the East China Sea is ours to do with as we please."
Buckner Bay proved to offer more excitement than the sweeps. Even the war's waning days possessed elements of danger; on 12 August a Japanese torpedo aircraft scored a hit on the battleship Pennsylvania, near Alaskas anchorage. Over the days that ensued, nightly sorties to avoid last-ditch suiciders took place. When the war did finally end in mid-August, the ship went wild with joy, as Alaskas chronicler wrote: "We knew that we would be going home far sooner than any of us had ever expected when we first set out the preceding January for the combat area."
Steaming thence to the Panama Canal, and completing her transit of the isthmian waterway on 13 December 1945, Alaska proceeded to the Boston Naval Shipyard, arriving on 18 December. There she underwent an availability preparing her for inactivation. Departing Boston on 1 February 1946 for her assigned permanent berthing area at Bayonne, New Jersey, Alaska arrived there the following day. Placed in inactive status commission, in reserve at Bayonne, on 13 August 1946, Alaska was ultimately placed out of commission, in reserve, on 17 February 1947.
The large cruiser never returned to active duty. Her name struck from the Naval Vessel Register on 1 June 1960, Alaska was sold on 30 June 1960 to the Lipsett Division of Luria Brothers of New York City, to be broken up for scrap.
Alaska was awarded three battle stars for her World War II service. Sailing on her final wartime service was a newly commissioned officer, future astronaut Wally Schirra.