The Group were selected to fly the relatively new Martin B-26 Marauder. Early models of this type earned a maligned reputation as it possessed some undesirable flight characteristics which contributed to several fatal accidents, but by the time the 386th received their aircraft various modifications had been incorporated and its performance greatly improved. In action it proved to have a good safety record.
In the meanwhile the Ground Personnel travelled to Camp Kilmer, New York and two weeks later en-trained for Pier 79 on the Hudson River and embarkation on the Queen Elizabeth now a troopship bound for the U.K. The Queen Elizabeth arrived at Gourock, Scotland on 2nd June 1943. A railway journey through the night conveyed the men to their first base at Snetterton Heath, Norfolk where they arrived by mid-afternoon on 3rd June 1943. However, within a week they were on the move again to Boxted near Colchester, Essex where they arrived on 10th June 1943. The Group's arrival at Boxted initially was one of disenchantment as the base was still under construction.
Over the following seven weeks the group embarked on an intensive training programme covering aircraft recognition, flying control procedures, enemy fighter tactics, air-sea rescue and escape and evasion techniques. During this time squadron code letters were applied to each aircraft: RG-552nd sqd; AN-553rd sqd; RU-554th sqd; and YA-555th sqd.
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).
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.