On April 1943 VB-139 was established at NAS Ault Field, Whidbey Island, WA, under the operational control of FAW-6, as a medium bombing squadron flying the PV-1 Ventura. Ground school and familiarization flights in the Ventura continued at Whidbey Island until the end of July. During this period, the commanding officer, LCDR G. H. Hughes became ill and was relieved of command. On 22 July, the squadron was relocated to NAS Alameda, CA, where new instrument panels were installed in all of the aircraft. Upon returning to Whidbey Island, the squadron flight crews began training with a new instrument flying syllabus. On 1 October 1943 VB- 139 departed NAS Whidbey Island for its first combat tour in three five-plane sections, arriving at NAF Amchitka, Aleutians, between 7 and 10 October. The squadron then came under the operational control of FAW-4 and was assigned routine search sectors. Missions were generally uneventful but weather always posed a serious hazard. Yet despite the poor weather conditions, the ground crews always managed to have the Venturas ready for the next mission. On 1 November 1943, a three-aircraft detachment was sent to NAS Adak, AK, for patrol duties and special training. On 8 December, three other squadron aircraft relieved this detachment. 

The first detachment continued on to a new assignment at NAS Attu, Aleutians. On 10 December 1943 the entire squadron relocated to Casco Field, NAS Attu, relieving VP-136. 

Routine searches out to 350–550 miles were conducted until 19 January 1944 when the squadron undertook several photographic reconnaissance and bombing missions over the northern Kurile Islands.