During the Invasion of Poland in 1939, he served with Escadre No. 111, assigned to the Pursuit Brigade and defending the Warsaw area. On 3 September his PZL P.11c fighter was damaged in combat but he successfully bailed out. During the campaign he shot down a Hs 126 on 8 September as a 'shared' victory. On 17 September he and other pilots were ordered to evacuate to Romania. There he was interned, but escaped and travelled to France by sea. After training on French aircraft, he was assigned to a flight commanded by Kazimierz Kuzian flying Morane MS-406 fighters protecting aircraft works around Nantes. However, Ferić saw no air combat. After the fall of France, Ferić evacuated in June 1940 to Great Britain. After advanced training at an RAFOTU he was assigned to the newly formed Polish No. 303 Polish Fighter Squadron, based at RAF Northolt flying Hawker Hurricanes and entering service in the Battle of Britain on 31 August 1940. On his first day of combat he shot down a Messerschmitt Bf 109. On 2 September he probably shot down another one, but his plane was damaged and he made a forced landing. On 6 September he shot down another Bf 109, and on 15 September a Bf 109 and Bf 110. On 27 September he shot down a Bf 109 and a Heinkel He 111, and on 5 October a Bf 109. After an operational break the squadron was back in combat in January 1941, flying Supermarine Spitfires on missions over France. On 22 June during a bomber escort he shot down a Bf 109, and on 27 June damaged another. In October he was sent to a six-month rest tour to an Operational Training Unit as an instructor, but after three months he volunteered to return to a combat posting. Ferić returned to No. 303 Squadron in January 1942. On 14 February, he was killed at RAF Northolt after his Spitfire broke up at and the resulting G-forces as the aircraft corkscrewed held him inside and prevented him bailing out. He is buried in Northwood Cemetery. Mirosław Ferić was the 11th ranked Polish fighter ace with 8 and 2/3 confirmed kills and 1 probable kill. From September 1939 he had kept a personal diary, which became No.303 Squadron's unit history.
