The start of the war led to the dissolution of the treaty system, but the dramatic need for new vessels precluded a new design, so the Clevelands used the same hull as their predecessors but were significantly heavier.

Following the start of World War II in September 1939, Britain announced it would suspend the treaty for the duration of the conflict, a decision the US Navy quickly followed.

[2] The ship's belt armor ranged in thickness from 3.5 to 5 in (89 to 127 mm), with the thicker section amidships where it protected the ammunition magazines and propulsion machinery spaces.

Another round of initial training followed in the Chesapeake from 23 April, including night firing practice, refueling at sea, and fighter director exercises.

The ship continued to operate off the Sicilian coast for the next nine days, providing fire support to ground forces as they fought their way inland, and protecting minesweepers as they cleared Axis mines from the area.

Birmingham was detached from the carrier group on 5 October to carry out shore bombardments of the island, targeting coastal batteries and storage dumps.

Throughout the afternoon and early evening, Birmingham and her sister ship Mobile detected a total of thirteen Japanese aircraft in the distance, but none of them attacked the Allied flotilla during this period.

Almost immediately after, another aircraft hit Birmingham with a torpedo on her port bow, blowing a 30 ft (9.1 m) hole and causing significant damage to the hull structure.

The ship's damage control teams quickly moved to contain the flooding and suppress fires from both hits, but a second Val made an attack run at Birmingham.

[3] The ship was dry docked in Pearl Harbor for repairs to her hull, and on 18 December she departed for the Mare Island Navy Yard in San Francisco, California, arriving there four days later.

On 3 June, the ship returned to Purvis Bay, by which time some fifty men aboard the vessel were suffering from bacillary dysentery.

The next day, she sortied as part of the escort for a convoy of transports and Landing Ships, Tank bound for the Marshall Islands, which were being used as the staging ground for the upcoming invasion of the Marianas.

The next day, Birmingham cruised off Garapan to cover UDTs on the beach and engaged Japanese coastal artillery and anti-aircraft guns in the area.

The ship received light damage to her upper works, but quickly returned fire, and over the course of the next two hours, silenced most of the guns and destroyed two ammunition dumps being used to supply them.

The Fast Carrier Task Force moved on to attack airfields in the southern Philippines, both to draw Japanese attention away from Palau and to neutralize aircraft that might interfere with the invasion.

During one of these raids, aircraft spotted a Japanese convoy of small coastal vessels off Mindanao; Birmingham, her sister Santa Fe, and the destroyers Laws, Longshaw, Morrison, and Pritchett were detached to intercept it.

The Fast Carrier Task Force arrived off the Ryukyus on 10 October and inflicted significant damage to Japanese aircraft and installations on the islands.

Japanese air forces launched a series of counterattacks on 24 October, and during one of these, a Yokosuka D4Y dive bomber scored a hit on Princeton that caused serious damage and several large fires; Birmingham and the three destroyers Morrison, USS Gatling (DD-671) and Irwin remained with the stricken carrier after she fell out of formation.

The destroyers initially attempted to come alongside and spray the burning carrier to help the ship's crew suppress the fires, but they repeatedly collided with Princeton in the heavy seas.

The blast destroyed much of the carrier's stern, throwing debris all along Birmingham's starboard side and inflicting grave casualties among the cruiser's crew.

Birmingham eventually arrived back at Mare Island in early November for repairs; during this period, she also received modifications to allow her to serve as a flagship.

Over the next week, her crew took part in anti-aircraft gunnery drills, practicing operating her seaplanes, and other exercises, before departing on 4 February to rejoin the fleet.

[3] On 5 March, the heavy cruiser Salt Lake City replaced Birmingham in the shore bombardment unit, and the latter vessel departed for Ulithi.

Birmingham was among the vessels assembled to block the Japanese flotilla should it break through; she and two cruisers and ten destroyers took up a screening position on the right flank of the Allied fleet.

At 19:11, Birmingham received news that American carrier aircraft had sunk Yamato, two light cruisers, and three destroyers, neutralizing the threat to the invasion beaches.

She resumed bombardment duties the next day, remaining on station off the island until 12 April, when she was recalled to help defend the main fleet from a major Japanese air attack.

On 4 May, another major Japanese counterattack appeared, and at around 08:40, a Nakajima Ki-43 Hayabusa kamikaze made a diving attack on Birmingham; the pilot approached from such a steep angle that only the 20 mm guns could elevate high enough to engage the aircraft, and they lacked the power to destroy the plane before it crashed into the ship.

The blast destroyed the ship's sick bay, penetrated three deck levels, and tore a hole in the hull below the waterline on the starboard side.

She emerged from the shipyard on 22 July, after which she took on ammunition, fuel, and stores before embarking on combat training in Hawaiian waters in preparation to resume operations against Japan.

She departed Pearl Harbor on 12 August and joined TG 12.3, which was steaming to Wake Island, where she was to shell the isolated Japanese garrison there to practice gunnery drills.