After training in the United States, it moved to England in March 1944, helping prepare for Operation Overlord by attacking targets in France.

The following month, it moved to Walterboro Army Air Field, South Carolina, where it began to fly the Republic P-47 Thunderbolts, with which it would be equipped for the rest of World War II.

[1][3] The squadron arrived at its first station in the theater, RAF Christchurch, England in early March 1944 and flew its first combat mission the following month.

The 509th helped prepare for Operation Overlord, the invasion of Normandy, by striking military airfields, and lines of communication, particularly bridges and railroad marshalling yards.

[3] Toward the end of June, the squadron moved to Picauville Airfield, France, and for the rest of the war concentrated on providing close air support for ground forces.

It supported Operation Cobra, the breakout at Saint Lo in July with attacks on military vehicles and artillery positions.

After immobilizing leading and trailing elements of the 3-mile (4.8 km) long column, the rest of the tanks and trucks were systematically destroyed with multiple sorties.

[4] Its operations from D-Day through September 1944 supporting the liberation of Belgium earned the squadron a citation in the Order of the Day of the Belgian Army.

The squadron received a Distinguished Unit Citation for action on 24 September 1944 when the 4th Armored Division experienced a counterattack by enemy forces and urgently needed air support.

[1][6] The following year, the squadron replaced its Sabres with Convair F-102 Delta Daggers, which were armed with AIM-4 Falcons and equipped with data link for intercept control.

In March 1962, the American radar unit at Pleiku Air Base began to detect unknown aircraft entering South Vietnamese airspace.

On 5 August 1964, six F-102s deployed from Clark to Da Nang Air Base in the northern part of South Vietnam.