Why did the "Torch" P-40Fs carry a flag on the fuselage?

During Operation Torch, the American invasion of North Africa, those P-40Fs were catapulted off a United States aircraft carrier with United States Army Air Forces (USAAF) pilots. Opposing them, French pilots of GC II/5 fought against United States Navy Grumman F4F Wildcats under the flag of Vichy France, allied with Germany. Aircraft carrying yellow-outlined roundels sometimes had American flags added in front of the roundels, in an attempt to deter Vichy forces from shooting them down. A photograph from those days shows Daniel Rathbun taking off in his P-40 fighter from the USS Chenango (CVE-28) heading for land for combat operations in Morocco, around 10 November 1942, with the American flag markings and the catapult bridle still visible behind the aircraft.

The yellow outline on the roundels was used on the idea that it would reduce instances of Americans shooting down unfamiliar British aircraft. It produced no significant results, and friendly-fire incidents continued. By June 1943 the yellow ring had been abandoned, as the aircraft switched to the star-and-bars insignia with a red outline.

Hostilities lasted only three days: on 11 November 1942, Vichy French forces in North Africa swore loyalty to General Charles de Gaulle, commander of Free France. On 8 January 1943, the newly reconstituted Free French air force formally received its first frontline combat aircraft in Casablanca, Curtiss P-40Fs, delivered by the USAAF.