On her first cruise with the fast carriers, she screened them against enemy air attack while their planes made three raids against targets in the enemy's home islands and the Ryūkyūs. On 8 June, TF 38 aircraft hit Kanoya on Kyūshū — the home of Japanese naval aviation. The next day, they struck the Ryukyu Islands — specifically Okino Daito, located a little over 200 miles west of Okinawa. The third and final strike of her first combat cruise came on 10 June and provided the cruiser with her initial opportunity to join the fray. While TG 38.1 aircraft bombed and strafed the airfield on Minami Daito, the ships in the screen — Topeka among them — moved in and took the other installations under fire. At the conclusion of that action, Topeka moved off with the rest of TG 38.1 bound for San Pedro Bay, Leyte.
After spending the latter half of June at Leyte for relaxation and replenishment, the light cruiser returned to sea on 1 July with TF 38 for the final six-week carrier sweep of the Japanese home islands. The task force made a fueling rendezvous on the 8th and then began a run-in toward Tokyo which the American planes bombed on 10 July. Next, the ships moved north to Honshū and Hokkaidō for a two-day antishipping sweep of the area around Hakodate and Muroran. They retired from the area for another fueling rendezvous on the 16th, but returned to the vicinity of southern Honshū and resumed the aerial blitz of Tokyo on the 17th and 18th. On the night of the latter date, Topeka had another opportunity to strike the enemy directly when she joined Atlanta (CL-104), Duluth (CL-87), Oklahoma City, and the destroyers of DesRon 62 in an antishipping sweep of the entrance to Sagami Nada near the sea approaches to Tokyo. During that sweep, she fired her guns at Japanese installations located on Nojima Zaki, the point of land which marks the eastern terminus of the entrance into Sagami Nada. Completing another replenishment retirement between 19 July and 23 July, the task force resumed its air raids on central Japan with two extensive forays against shipping in the Inland Sea on the 24th and the 28th, respectively.
A typhoon at the end of July forced the task force to take evasive action and postpone further air operations until the second week in August. At that time, Topeka steamed north with TF 38 while the carriers moved into position to send sortie after sortie against heavy concentrations of enemy aircraft on northern Honshū. Those raids — launched on 9 August and 10 August — proved eminently successful, wiping out what was later learned to be the transportation for 2,000 shock troops being assembled for a one-way, suicide mission to destroy the B-29 bases on Tinian. The carrier planes paid return visits to Tokyo on the 12th and 13th and were taking off to repeat those attacks when a message arrived on the 15th, telling of Japan's capitulation.
Topeka patrolled Japanese waters until mid-September, at which time she entered Tokyo Bay. She remained there until 1 October, the day she began her homeward voyage to the United States. The cruiser stopped briefly at Okinawa on the 4th to embark 529 veterans and resumed her eastern progress on the 5th. On 19 October, she arrived in Portland, Oregon, and disembarked her passengers. Ten days later, she steamed south to San Pedro, California, for overhaul. On 3 January 1946, the warship put to sea to return to the Far East. She reached Yokosuka, Japan, on the 24th and began duty supporting American occupation forces in Japan, China, and in the Central Pacific islands. During that tour of duty, which lasted until the following fall, she called at Sasebo, Japan, Tsingtao and Shanghai in China; Manila in the Philippines; and Guam in the Marianas. The cruiser returned to San Pedro on 20 November.
Following an overhaul and operations along the west coast, she headed back to the Orient on 22 September 1947. Upon her arrival at Yokosuka, Japan, on 10 October, she became a unit of TF 71. Operating from bases at Shanghai and Tsingtao. the warship patrolled the north China coast while civil war raged on shore between Nationalist and communist factions. She concluded that duty early in March and entered Nagasaki, Japan, on the 8th. Following visits to Sasebo and Kure, Topeka sailed for the United States on 25 April and arrived in Long Beach, California on 7 May. Later that month, she moved to Pearl Harbor for a four-month overhaul at the completion of which she returned to the west coast. Late in October, the warship resumed local operations out of Long Beach and out of San Diego. She remained so occupied until February 1949. On 25 February, she arrived in San Francisco to prepare for inactivation. Topeka was decommissioned there on 18 June 1949 and berthed with the local group of the Pacific Reserve Fleet.
In March 1964, she embarked upon her third deployment to the western Pacific since being recommissioned. That deployment began routinely enough with fleet exercises in May and calls at Japanese, Taiwanese, Malaysian, and Philippine ports. However, in August, North Vietnamese torpedo-boats attacked Maddox (DD-951) on the 2d and then returned to attack Maddox and Turner Joy (DD-731). This action — known as the Gulf of Tonkin incident — gave the remaining part of Topeka's deployment a more wartime character. Topeka cruised the waters of the Gulf of Tonkin while American involvement in the Vietnam War began to gather momentum. It was more than a year, though, before she steamed into war in earnest. Late in October, she started for home and reentered Long Beach near the end of the second week of November. For the next 12 months, she viewed the developing war from afar-operating out of west coast ports, undergoing repairs and modifications, and conducting exercises with the 1st Fleet.
On 29 November 1965, however, she headed back to the western Pacific for the first deployment during which her primary mission was to support the American and South Vietnamese forces fighting the communists. On that tour of duty, she served as the flagship for the Commander Cruiser-Destroyer Group, 7th Fleet. In that capacity the ship operated in the South China Sea and in the Gulf of Tonkin providing naval gunfire support for the troops ashore and supporting carrier air operations by conducting search and rescue missions for downed aircrews. She punctuated tours of duty in the combat zone with port visits to Yokosuka, Japan, Hong Kong, and the Philippine ports of Manila and Subic Bay. Her six-month deployment ended on 28 May 1966 when Topeka reentered Long Beach.
Five months of normal west coast operations — upkeep, training exercises, and the like — followed. On 31 October, the guided missile cruiser entered the naval shipyard for an overhaul during which her weapons systems were updated, and her engineering plant was overhauled. On 13 March 1967, she completed the yard overhaul and began sea trials and, later refresher training. She finished those evolutions early in June and resumed local operations. On 1 August, the warship put to sea from Long Beach for her first deployment to the Mediterranean Sea. She stopped at Norfolk on 12 August and 13 August to embark the Commander, Cruiser-Destroyer Flotilla 12, and his staff and then sailed for Palma de Majorca on the 14th. On the 20th, Topeka joined the 6th Fleet and, on the 22d, relieved Galveston (CLG-3) as flagship for TG 60.2. During her five months with the 6th Fleet, she ranged the length of the "middle sea." In late September and early October, the warship participated in NATO exercise Eager Beaver, conducted in the eastern end of the Mediterranean. In mid-October, she conducted operations in the Ionian and Tyrrhenian Seas on her way back to the western end.
In January 1968, she concluded her first tour of duty in the Mediterranean with another NATO exercise — this one an amphibious operation. On the 12th, she was relieved by Columbus (CG-12) at Rota, Spain. The cruiser then headed back to the United States. After stops at Puerto Rico and in the Panama Canal Zone, Topeka reentered Long Beach on 29 January.
On 2 February, the warship began a five-week availability at the Long Beach Naval Shipyard. The guided missile cruiser departed Long Beach again on 15 March, bound for her new home port, Mayport, Florida. After arriving at her destination on 21 March, Topeka remained in port for upkeep until 6 May when she returned to sea for refresher training at Guantánamo Bay, Cuba. Returning to Mayport on the 26th, the ship began preparations for another deployment to the Mediterranean — the last deployment of her career.
Topeka departed Mayport on 29 June and, after gunnery exercises at Culebra Island near Puerto Rico, she headed across the Atlantic. On 9 July, she relieved Columbus at Málaga, Spain, and began 6th Fleet operations. The warship's final deployment proved to be routine in nature. She visited ports all along the Mediterranean littoral and conducted operations in all portions of the middle sea from the Aegean and Ionian Seas in the east to the French Riviera ports in the west. Spain, Italy, Greece, Turkey, and France — as well as the islands of Malta, Crete, and Majorca — provided her with interesting ports of call. Topeka concluded her assignment with the 6th Fleet on 9 December at Rota when she was relieved once again by Columbus. That same day, she headed for Mayport, arriving 10 days later.
On 30 January 1969, Topeka steamed out of Mayport and proceeded north for inactivation. After a stop at Yorktown, Virginia, to off-load her ordnance, she arrived in Boston on 5 February. There, she completed inactivation preparations; and, on 5 June, Topeka was placed out of commission. The warship was towed to Philadelphia and was berthed with the reserve fleet group there.