S/Ldr. J. Brzezinski joined 317 Squadron as a PIlot Officer and soon found promotion to Flying Officer, and then Flight Lieutenant.
He was invested, along with other 317 Squadron pilots, with the "Krzyz Walecznych" on 11th November 1941, by the President of Poland during a visit to Exeter.

Just after 13.00 hrs on 18th December, Josef flew as Red Two on an operational flight to provide cover for bombers returning from a mission over Brest. Nine Me109s attacked the Halifax bombers, and Red, Yellow and Blue sections dived in to combat with them. Four Me109s were dispatched rapidly by the squadron, one by Josef who fired a one second burst at 300 - 500 yards at an Me 109 as it passed from right to left, giving fill deflection, smoke instantly appearing. The Messerschmitt turned right, diving down out of control. The remaining Me109s broke away and fled to French coast, and the Halifaxes continued their journey home without fiurther hindrance. Unfortunately the squadron had arrived too late to help a Stirling bomber, which was shot up and crashed in flames into the sea. (An Air Sea Rescue operation was launched, headed by a Lysander and escorted by two Spitfires from 317 Squadron and three Spitfires from 87 Squadron, and spotted a distress flare. They had located the crew numbering seven in a rubber dinghy by mid-afternoon.) They were picked up by an MTB and two launches.

On 1st March 1942, Josef became the commanding officer of 317 Squadron after S/Ldr Szczesny was appointed to H.Q. Fighter Command.

On 15th March 1942, the squadron left Exeter to rendezvous with fighters from 306 Squadron to assist bombers over the French coast. At 17.10hrs they returned, setting course for Predannack where they intended to land.
On arrival in the vicinity the cloud and mist being so low they searched for 15 minutes in an effort to find the drome, but without success. It was decided to proceed to Bolthead although the pilots were now losing sight of the another owing to the poor visibility. On arrival in the vicinity conditions were very bad the drome being completely covered with thick cloud. In fact one pilot F/O Koc with the aid of instruments flew over the drome at 20 feet but was unable to see it. The pilot, although his gauge indicated that he had only 7 gallons of fuel left, decided to make for Exeter where he made a successful landing at 18.04 hours. All aircraft were now very short of fuel the result was that they had to crash land in the vicinity of Bolthead. The only other successful landing was made by F/Sgt Brzeski at Newquay. The remaining 10 aircraft all crash landed in the Bolthead area.
(Squadron Leader) Brzezinski's aircraft struck the side of a cliff and he was killed instantly.

He was buried at Higher Cemetery in Exeter, on 19th March 1942. The funeral was attended by the Station Commander. Group Captain Edward-Jones and many representative from the other squadrons, and also by representatives of the Polish Army supported by as many of the squadron personnel that could be spared.

On 4th June, 1941, P/O Brzezinski went to London as witness in a Court Martial, and returned to the squadron the following day.
On 1st July 1941, F/O Brzezinski was sent with F/Lt Kowalczyk to Blackpool on temporary duty.