army as it advanced towards Odessa. In 1942, they were replaced by Junkers Ju 88 bombers, allowing the survivors to be transferred to the advanced training role. Second World War On 28 August 1939, the French Air Force initiated the mobilisation of its units, including those equipped with the Potez 630 series. Due to requests from French Naval Aviation some Potez 631 aircraft were soon diverted to replace their Dewoitine D.371 fighters. In February 1940, a new war plan, Plan V bis, was adopted; under this plan, nearly all Potez 630 and a number of Potez 631 aircraft were retired from front line service, with some of the 630s converted to become dual-control training aircraft. That same month, it was decided to rearm the majority of Potez 631s, replacing their original armament of one cannon and one machine gun with two cannons and four underwing machine guns for the purpose of conducting ground attack missions; however, progress on this was relatively slow. The French Air Force found a use for the Potez 633 aircraft as conversion trainers for units that had received the Breguet 691 attack aircraft. On 20 May 1940, three Potez 633s took part in a strafing mission against German troops near Arras. This was the type's only operational mission over France as two days later the aircraft was withdrawn from front-line service. A small number of Potez 633 originally destined for China were commandeered by the French colonial administration in Indochina and saw limited action in the brief French-Thai War in early 1941. Parked in the open ground, a number of them were destroyed by Thai Hawk 75N strafing during an air raid at Siem Reap. Once active combat had begun, the Potez 631 had quickly proved to be an ineffectual interceptor; it was slower than some German bomber aircraft and 130 km/h slower than the Messerschmitt Bf 109E fighter. Perhaps the most successful unit operating the Potez 631 was the Flottille F1C of the French Naval Air Arm; between 10–21 May 1940, aircraft of the unit shot down 12 enemy aircraft in exchange for 8 of their own losses prior to its withdrawal from active combat. At one point, the Potez 637 was the only modern aircraft equipping the Groupes de Reconnaissance (GOA), which had long been equipped with obsolete aircraft. From November 1939 onwards, the first units to convert to the Potez P.63.11 were each