Montgomery would be more apt to throw British reserves into the battle under such a command arrangement. The next morning Smith brought up the matter in the Supreme Commander's usual meeting with his staff. Eisenhower in his turn telephoned Bradley, who agreed to the division of command.
The new army group boundary line, now ordered by Eisenhower, would extend from Givet, on the Meuse, to St. Vith. (That both these locations would be Montgomery's responsibility was not clarified until nearly twenty-four hours later.) The reorganization placed the U.S. First and Ninth Armies under Montgomery's 21 Army Group. Bradley would command all forces to the south of the salient-which in effect meant Patton's Third Army-and eventually he might add Devers' 6th Army Group. The reorganization required a like shift in the Allied air forces, meaning that the U.S. IX and XXIX Tactical Air Commands (Maj. Gen. Elwood R. Quesada and Maj. Gen. Richard E. Nugent) were put under the operational control of the British Second Tactical Air Force commanded by Air Chief Marshal Sir Arthur Coningham. Because the British had very strong forces of fighter-bombers, enough of these planes were taken from IX Tactical Air Command to give Brig. Gen. Otto P. Weyland's XIX Tactical Air Command, slated to support Patton's counterattack into the German bulge, ten fighter-bomber groups. 
The decision to pass the U.S. First and Ninth Armies to British command must have been hard to make, since both Eisenhower and Smith were acutely conscious of the smoldering animosity toward the British in general and Montgomery in particular which existed in the headquarters of the 12th Army Group and Third Army, not to mention the chronic antiBritish sentiment which might be anticipated from some circles in Washington.  This decision involved no question of Bradley's ability as a commander-that had been abundantly proven-but rather was a recognition of the communications problem presented by the German thrust between Bradley's headquarters in Luxembourg City and Hodges' headquarters, which had been moved on the 19th from Spa to Chaudfontaine.
Face-to-face discussion between Bradley and Hodges-let alone Simpson-so needful if the army group commander was to give the continuous encouragement and counsel demanded in these trying days, was already difficult. If German raiders crossed the Meuse, it might become impossible. Bradley had last visited Hodges in the early evening of the 17th by motoring directly from Paris. Further visits would involve traversing three sides of a square: west from Luxembourg across the Meuse (and perhaps as far west as Reims), north into Belgium, then east again behind the none too certain American front. Telephone and radio contact still existed; indeed, Bradley talked half a dozen times on the 18th with Hodges and General Kean, the First Army chief of staff, and at least twice on the 20th.
 Daily notes kept by the Chief of the Air Staff, SHAEF, Air Marshal James M. Robb on the meetings held in the Supreme Commander's office SHAEF (Main), in OCMH files (hereafter cited as Robb Notes); SHAEF (Main) files: Montgomery to Eisenhower.
Pogue, The Supreme Command, pp. 378-80 and n.: Eisenhower, Crusade in Europe, p. 355.