Brill made few contacts worthy of torpedo fire and consequently had to settle for damaging an unidentified ship of approximately 1,000 gross register tons as her only score.

Brill spent a week at Pearl Harbor undergoing voyage repairs and torpedo training before getting underway for the Mariana Islands on 28 January 1945.

At first, she encountered no Japanese ships, but on 20 February 1945, just after Brill sank a floating naval mine with gunfire, her watchstanders saw a torpedo wake approaching on her starboard quarter.

Both torpedoes passed by her on her starboard side before she moved out of range, submerged, and headed hack to search in vain for what she assumed was a Japanese submarine that had attacked her.

On 15 March 1945, while providing lifeguard services for American bombers attacking Hainan Island, Brill maneuvered to avoid another torpedo fired at her, presumably by a Japanese submarine.

On 21 March 1945, Brill rendezvoused with the submarine USS Gurnard (SS-254) to bring aboard an Australian Army officer and a native Malayan guide for a special mission on Sakala Island.

She terminated her patrol at Subic Bay on Luzon in the Philippines, where she underwent a refit alongside the submarine tender USS Howard W. Gilmore (AS-16).

By this time, Brill was inside the 10-fathom (60 ft; 18 m) curve and the onset of darkness ruled out using her deck guns to sink the patrol vessels, so she broke off the attack.

There, she served as a unit of Submarines, Philippine Sea Frontier, until January 1946, when she received orders to Pearl Harbor for repairs to her diesel engines.

After calling at Pearl Harbor, she got back underway on 5 February 1946 with only three of her four engines in operation, heading east to San Diego, California, for a period of shore leave and upkeep.

Taking up a position in the Alenuihaha Channel, the submarines attempted to intercept the battleship as she made a high-speed run between Maui and the island of Hawaii.

Although Iowa enjoyed land-based air cover and tried to throw off her pursuers by several radical course changes, the submarines still achieved four "successful" mock attacks against the battleship.

[5] Brill again resumed training exercises in Hawaiian waters with Submarine Squadron 5 until 4 September 1947, when she departed Pearl Harbor for San Diego.

Leaving the shipyard early in 1948, she completed refresher training and departed on 24 February 1948 for Naval Submarine Base New London in Groton, Connecticut, where she arrived on 16 March 1948.