She escorted a troop convoy to the Pacific in early 1942 before returning to the South Atlantic where she patrolled for German commerce raiders and blockade runners.

At deep load she carried 1,852 long tons (1,882 t) of fuel oil that provided her a range of 6,500 nautical miles (12,000 km; 7,500 mi) at a speed of 10 knots (19 km/h; 12 mph).

Milwaukee was initially built with the capacity to carry 224 mines, but these were removed early in her career to make more space for crew accommodations.

Three years later, during Fleet Problem XIV, Milwaukee was spotted by fighters from the aircraft carrier Saratoga and "sunk" by some of the opposing cruisers.

[3] While steaming north of Hispaniola and Puerto Rico on 14 February 1939, Milwaukee discovered the deepest place in the Atlantic Ocean.

[7] Cruiser Division 2 was ordered to patrol the Atlantic between Trinidad, the Cape Verde Islands and the eastern bulge of Brazil in April, although Milwaukee was not immediately available.

The ship, escorted by the destroyers Somers and Jouett, began her first patrol in May, making a port visit to Recife, Brazil, on 1 June, before returning to San Juan, Puerto Rico.

[12] Milwaukee, commanded by Captain Forrest B. Royal, was being overhauled in the Brooklyn Navy Yard when the Japanese attacked Pearl Harbor on 7 December.

On 19 May she received an SOS from the Brazilian cargo ship SS Commandante Lyra, which had been torpedoed by the Italian submarine Barbarigo off the coast of Brazil.

Reinforced by her sister Omaha and the destroyer McDougal, the fires were brought under control, cargo was jettisoned to lighten the ship, and Commandante Lyra was towed to Fortaleza, Brazil.

[3] Shortly after, on the night of 20 May, she was attacked by the Barbarigo, commanded by Enzo Grossi (who mistook her for a "Maryland- or California- type battleship") with two torpedoes, which missed and were not even noticed by the American ships; however, Grossi claimed to have sunk his target, and was promoted to Capitano di Fregata (Commander) and decorated with the Gold Medal of Military Valour and the Iron Cross.

[13] Rear Admiral Oliver M. Read assumed command of Cruiser Division 2 in October and hoisted his flag aboard Milwaukee.

[14] On 21 November, Milwaukee, her sister Cincinnati and the destroyer Somers intercepted the German blockade runner Anneliese Essberger.

She was commissioned in the Soviet Navy as Murmansk and performed convoy and patrol duty in the Arctic Ocean for the remainder of the war.