Priller joined the military service in the Wehrmacht in 1935. Initially serving in the Army, he transferred to the Luftwaffe in 1936. Following flight training, he was posted to Jagdgruppe Wiesbaden, this unit was later designated I. Gruppe Jagdgeschwader 334 and then became I. Gruppe of JG 133 on 1 November 1938.

He was then transferred to Bad Aibling, serving with I. Gruppe of Jagdgeschwader 135, a unit, which on 1 May 1939 formed I. Gruppe of Jagdgeschwader 51 and was commanded by Major Max Ibel. Here he served as the Nachrichtenoffizier (communication officer) of I. Gruppe.

In July 1939, he was posted to I. Gruppe of Jagdgeschwader 71, here Priller was promoted to Oberleutnant on 1 September 1939. And on 1 November his unit was once more renamed, this time to II. Gruppe of JG 51.
On 20 October he was tasked with forming of 6. Staffel at Eutingen im Gäu. On 5 November 6. Staffel was officially created and became operational. On 9 February 1940, II. Gruppe was moved to Böblingen Airfield where it was subordinated to Jagdgeschwader 52 and tasked with patrolling the Upper Rhine region during the Phony War.

At the start of the attack in west on 10 May 1940 the II./JG 51 was based at Böblinen under the control of Stab/JG 54. During the first two weeks the Gruppen flew fighter sweeps and ground attack missions in the Elass area, however the number of enemy contacts was few.

It was not until the 6 Staffel was relocated to Flandern on 26 may that things started to heat up. And two days later Oblt. Priller manage to score his Staffel first abschuss over Dunkirk. His firs victim this day was a Spitfire downed at 13.07 hours and three minutes later a Hurricane fell before his guns. In all the 6./JG 51 downed four enemy aircraft north west of Dunkirk this day. For his achievement, Priller was awarded the Iron Cross 2nd Class (Eisernes Kreuz zweiter Klasse) on 30 May 1940.

Another eight machines was claimed by the II.Gruppen while fighting over France without any own losses in air combat and Priller would downed four of them. One Currtiss was claimed in the evening hours over Dunkirk on 2 June. Then followed two Blendheims over Abbeville on 8 June, shot down within two minutes. And finally, Oblt. Josef Prillers last abschuss was filed on 25 June, another Spitfire that was shot down 8 km Northwest of Desvres. Hereby Josef Priller reached a total of six confirmed victories during this campaign.

This profile was one of six profile made during the week. Four allied machines and two Bf 109 Emils. I guess this profile woud be included in profile book No 18.