It was briefly activated in 1947, but budget considerations resulted in reductions of Air Force strength in Fiscal Year 1949, and the squadron did not equip or man.

[1][3][4] At the time of the Japanese Attack on Pearl Harbor, the squadron began flying antisubmarine patrols and watching for signs of an invasion.

In early May, the 12th Group deployed to Stockton Army Air Field, California, where half its crews stood alert during daylight hours.

[6][5] In June 1942, while in the United States for a conference with President Franklin D. Roosevelt, British Prime Minister Winston Churchill made an urgent plea for military aid to help stop Erwin Rommel's Afrika Korps from overrunning Egypt, the Suez Canal and the Arabian oil fields.

The unit's first missions were flown to support forces opposing Rommel's final effort to break through to the Suez Canal at the Battle of Alam Halfa between 31 August and 4 September 1942.

By 4 November, Rommel began withdraw and the squadron's main targets became columns of tanks, trucks and troops retreating to the west.

[12] American forces under General Dwight D. Eisenhower landed in Algeria and Morocco, and were met by German divisions under Rommel's command.

[13] The squadron's actions during the north African campaign earned it a Distinguished Unit Citation for its operations from primitive landing grounds under difficult weather and terrain conditions and, despite repeated enemy attacks on its advanced positions and limited resources, made a major contribution to the defeat of enemy forces in the Middle East.

The group's advance party boarded LSTs for Licata Sicily, where they set up their first base in Europe at Ponte Olivo Airfield, flying their first mission from Italy on 5 August.

Later in August, the group moved to Gerbini Airfield, from which it struck bridges, tunnels and other targets to support Operation Baytown, the invasion of southern Italy.

Although some in the group hoped the move was a withdrawal from combat, the ships sailed east, passing through the Suez Canal on the way to India.

[15] The 12th Group moved to India to help the British Fourteenth Army repel a Japanese invasion from Burma toward Imphal, threatening the whole subcontinent and the Indian Ocean.

[e] The squadron flew its first mission as part of Tenth Air Force, bombing Japanese supply dumps at Mogaung, Burma, on 16 April 1944.

[16] In April, Japanese forces that had broken out of the Burma mountains the previous month surrounded two Indian divisions at Imphal.

[16] The last major mission of the squadron was an overnight where the crews spent the night under the wings of their B-25s at Rameree, near Rangoon, and took off the next morning to bomb Ban-Takli airfield north of Bangkok, Thailand.

The squadron's aircrews flew the A-26s to Frankfurt, Germany, and the rest of the group waited at Fenny Airfield until they went to Karachi Airport in December to return to the United States.

[citation needed] On return to United States in January 1946, the squadron was inactivated at the port of embarkation the day after it arrived.

On 31 October 1952 USAF Pilot Jimmy Priestly Robinson of the 561st Squadron was lost at sea after Operation Ivy testing.