he was assigned to No. 145 Squadron RAF, and became operational on 4 August 1940. On 8 August he shot down a Messerschmitt Bf 110 flown by Major Joachim Schlichting of V./LG 1 while flying with No. 601 Squadron (although he was never officially attached to the unit) and on 12 August a Junkers Ju 88 of KG 51. On 21 August he was transferred to the Polish-manned No. 303 Squadron, flying a Hawker Hurricane as "A" Flight commander. On 6 September he shot down a Bf 109 of JG 52. On 7 September he became Squadron Leader, after Zdzisław Krasnodębski was badly burned. On 15 September Urbanowicz claimed two Dornier Do. 17's of KG 2. On 18 September 1940 Urbanowicz was awarded the Silver Cross of the Virtuti Militari by the Commander-in-Chief of the Polish Forces, General Sikorski. On 24 October, he was awarded the Distinguished Flying Cross. On 27 September he was officially credited with shooting down four aircraft: two Ju 88s of KG 77, a Bf 109 and a Bf 110 of 15.LG 1. On 30 September he claimed three Bf 109s (one from stab. JG 26, one of II./JG 53 and one of 4.JG 54) and one Dornier Do 17 of KG 3. Despite his success Urbanowicz was never popular at the Polish headquarters and on 21 October he was forced to hand over command of the Squadron to Zdzisław Henneberg. During the Battle of Britain, he claimed 15 confirmed kills and 1 probable, which made him one of the top Polish aces (second only to Stanisław Skalski) and among the top ten Allied aces of the battle. Between 15 April 1941 and 1 June 1941 he commanded the 1st Polish Fighter Wing based at RAF Northolt, before being posted to staff work at No. 11 Group RAF HQ. In June 1941 he was assigned as the 2nd Air Attaché in the Polish Embassy in the United States. In September 1943 Urbanowicz joined the USAAF 14th Air Force on attachment in China. On 23 October he joined the 75th Fighter Squadron of the 23rd Fighter Group ("Flying Tigers"). Flying a P-40 Warhawk he took part in several combat missions. On 11 December he fought against six Japanese Mitsubishi Zeros and claimed two shot down (these were actually Nakajima Ki-44 "Tojo" fighters of the 85th Sentai). According to his reports he also shot other airplanes over China,