On the 29th June 1943, the revised National Insignia was introduced. Two white rectangles were placed on either side of the cocarde and the entire device was bordered with red.

The first combat mission undertaken by the Group occurred on Friday 30th July 1943. All necessary personnel were alerted just after midnight and the crews were breakfasting by 0230 hours. Briefing for pilots, navigators, bombardiers and gunners was scheduled for 0300 hours when at that precise moment the lighting system failed. After a slight delay emergency lighting was installed and Col. L. Maitland resumed the briefing. The target was to be the Luftwaffe fighter airfield at Woensdrecht in South Holland. The 386th would fly a 24 ship formation, six aircraft from each squadron. Route out from base to Orfordness to rendezvous with eight squadrons of RAF Spitfires, altitude 12000 ft. Known flak batteries, radio call-signs, channels and expected weather forecast details followed. Meanwhile ground crews were engaged in removing ground locks, pitot-tube covers and starting auxiliary power units to assist in engine start-up. After engine run-up and final instrument checks the B26's taxied out along the perimeter track to active runway No. 22. On a green light from the Control Tower, Col. Maitland's lead aircraft lifted off at 0525 hours. He was followed at 30 second intervals by the other twenty three aircraft. On reaching the enemy coast evasive action was commenced in order to disrupt the tracking system of the enemy gun-layers. As the bomb-run began, the lead bombardier was unable to see the target due to sun dazzle and heavy haze. Col. Maitland ordered a second run at the target. Heavy flak caused damage to several aircraft. On return to Boxted the very excited and relieved crews were interrogated and results of this first mission were described as disappointing. Although two passes were made at the target, restricted visibility and up-sun heading on the bomb-run prevented most flights from bombing. The enemy losses were two destroyed and two probable.

Whenever conditions permitted, the Group continued to pound targets in Northern France and the Low Countries which included enemy airfields, rail and road networks and supply installations. On other occasions they were perfecting their skills in formation flying and techniques of bombing from medium altitudes (10,000 - 12,000 ft).

Missions were often executed in conjunction with other B26 groups, each supplying formations in boxes of 18, 36, or even 72 aircraft. Close fighter support was provided by Spitfires of 11 Group Fighter Command of the RAF which, on a typical mission, could number eight to ten squadrons.

In late September 1943, High Command decided to concentrate the four existing B26 groups at airfields in mid-Essex, the 386th BG being allocated to Station 164 Easton Lodge, Great Dunmow, a distance of 24 miles West of their recent base at Boxted. The Group carried out 28 missions from their Boxted base, the last one being on the 24th September to the airfield of Evereux-Fauville, France. Upon their return the Group relocated to their new base, Station 164.