The Air Command Post Afloat
Offensively air activity during the invasion was scheduled and controlled from the U.S.S. Catoctin, Amphibious Force flagship for the over all operation. Here XII Tactical Air Command (Advance) operated, charged with air protection of the Fleet and the beaches in the assault area, as well as with the continuation of its fighter-bomber and reconnaissance work against enemy ground forces. Its aircraft were based in Corsica, 150 miles away.
The Catoctin was a stand-by fighter direction ship for air defense. FDT No. 13 (fighter direction tender), a British LST, was responsible for control of defensive fighters on patrol over the assault area. HMS Ulster Queen was another stand-by fighter direction ship.
The 2d Air Combat Control Squadron (Amphibious), activated as an amphibious fighter control squadron to serve aboard headquarters ships, handled air control for the Air Task Force commander aboard the Catoctin during the assault phase. This unit reported on 16 March 1944 to the Commander of the U.S. Eighth Fleet, when invasion plans were already under way.
For the control of the numerous land-based aircraft necessary to the program, the communications and air control equipment on board were enlarged into a Joint Operations Room (JOR), where both naval officers and those of the 2d Air Combat Control Squadron were able to perform their various functions, including: control of air cooperation missions as directed by the air commander: standby control of fighter defense of the assault area as directed by the air defense commander; issuance of air raid warnings as directed by the naval commander; collection, evaluation, and dissemination of air information to all responsible officers.
The flexibility obtained by modifying the original JOR facilities was demonstrated by the fact that the exercise of control of air co-operation missions was assigned as an additional duty less than a week before D-day, while the further duty of issuing air raid warnings was assumed during DD-day. One week before D-day a full scale exercise, placing particular emphasis upon those communications which would be available to the air commander, proved highly valuable.
The decision to assign the control of offensive fighter-bomber missions to the flagship, while control of defensive fighter patrols remained with a fighter direction ship, proved to be sound. In the almost total absence of enemy air opposition, the supporting aircraft so controlled were able to give welcome aid to the quick establishment of the beachhead and the speedy advance of the ground forces.
The duties of the JOR as outlined above were operationally, and more specifically, broken down into four main subdivisions: control of tactical reconnaissance and fighter-bomber missions; furnishing information on movements and status of aircraft; air raid warning and alerting the fleet; stand-by for fighter direction. How these duties were discharged, and what they involved, may be briefly noted here.
Control of Tac/R and fighter-bomber missions
Tac/R flash reports were furnished by pilots of two Tac/R squadrons flying Corsica-based Spitfires and P-51's, by carrier-based Spits, and occasionally by returning fighter-bomber missions. These missions, scheduled by XII TAC, reported name and mission number to the Catoctin when entering the area. This information was placed on the Tac/R status board and the flight told to proceed with its next assignment.
When flyers spotted anything of interest the information was immediately called in to the deputy controller, who made out a standard report and passed it to the XII TAC operations officer for action. If accepted, the attack order number of the fighter-bomber mission to which the new target was assigned was placed on the report, which was given back to the deputy controller for transmittal to that mission when it checked in.
Fighter-bomber missions were flown by P-47's and P-38's based in Corsica and by carrier-based Hellcats and Wildcats. These missions, laid on by XII TAC, were given both a primary and an alternate target. They reported in to the Catoctin on Channel AC-3, giving name and attack order or mission number, which was immediately placed on the Fighter-Bomber Status Board. They were then told to attack either their primary or their alternate target, or to proceed on a special mission. This was necessary because the speed of the advance sometimes placed either or both of the briefed targets inside the bomb safety line. On other occasions, the special mission was given priority over the regular mission.
These special missions were usually against enemy transportation and were targets called in by Tac/R planes or received by XII TAC from the ground forces or other sources. The targets were given to the airborne planes in the clear since, due to the speed of operations, security did not demand encoding. Locations were given in Army grid, air grid, or by geographical references. On some occasions, if the Tac/R flight which reported the target was still in the vicinity, it was directed to lead the bombers to the target.
Here are a couple of examples of how this system worked. Spurtle Red Leader checked in and was told to proceed on his mission of armed recce. Three minutes later, Parkland Red Leader, returning from a bombing mission, called in a target of 20-plus boxcars and engines near Pertuis, which he could not take himself. This target was given at once to Spurtle Red Leader, who was told to call Parkland Red Leader on the same channel for directions. This was done and the target was successfully hit.
Alpaca Red Leader, a carrier-based Tac/R mission, called in a target of 20-plus armored vehicles east of St. Maximin which was given to Mallard Red, a carrier-based Hellcat mission of fighter-bombers just reporting into the assault area. Result--65 armored vehicles and troop carriers shot up. Confirmation of this was received a few minutes later when another Tac/R flight reported between 50 and 60 vehicles destroyed in that locality.
If any doubt remains about results from these missions against enemy transport, consider what happened on 10 other such attacks:
20-plus M/T destroyed near Digne
15-plus M/T bombed, one flamer, near Aix
150-plus RR cars hit
20 cars bombed, 30-car train strafed, north of Lake Bret
30 RR cars hit outside Avignon
45 boxcars left burning, two engines destroyed, near Cavaillon
1 turntable and 15 RR cars destroyed on D-9
2 barges bombed and strafed 20 miles west of Marseille
RR bridge and train bombed, 2 M/T hit north of Tarascon
10-plus M/T hit southeast of Avignon
During the four and one-half days the Catoctin was in control, approximately 300 fighter-bomber missions operated in the area. Of these, about 50 were antitransport missions given out by the controllers at the order of the Commanding General, XII Tactical Air Command.
Furnishing information on movements and status of aircraft
The JOR acted as a clearing house for all information concerning air operations in the assault area. This included movements of hostile aircraft; status of patrols, fighter-bomber, medium and heavy bomber, Tac/R, carrier-based aircraft, and night fighter missions; and results of these missions when they could be obtained through R/T interception. This information was obtained form six principal sources:
Monitoring of Operational Channels. All operational channels were manned by deputy controllers or monitors, and movements of aircraft were recorded on various status boards or in logs. A list of all call signs to be used in the operation was prepared in advance and aided in identifying missions.
Movements Liaison Officer. The MLO had advance information on most friendly missions entering or passing through the area. This included attack order number, time, number and type of aircraft, and objective. This information was supplied by XII TAC Operations aboard for the missions they scheduled, by signals received from the Strategic Command based in Corsica and Italy, and by the courier liaison officer.
Aircraft Carrier Liaison Officer. This officer advised the senior controller of the status of carrier-based aircraft, missions entering area, and the results of completed missions. He also passed back to the new carriers requests for additional missions or the assignment of new targets. He was in constant HF/RT contact with the carrier task force. This was invaluable, as carrier-based operations have many problems not common to land-based aircraft.
Radar. All information on air movements, both friendly and hostile, received on the filter table was passed to and displayed on the operations table and was available to all officers in the JOR.
Radio Intercept Service. Due to light hostile activity, there was little information from this source. However, more activity was reported than actually came into the area, despite considerable interference from W/T circuits.
Visual Observers. One visual controller and a recognition officer were located on the visual platform topside. They had a direct line to the senior controller and kept him advised of the movements and identity of all aircraft within visual range.
The information obtained from these sources was posted on various status boards in the JOR, entered in various logs, and furnished to interested persons as requested, or as conditions demanded.
Air raid warning and alerting the Fleet
This duty, originally assigned to FDT #13, was assumed by personnel aboard the Catoctin on D-day evening. Twenty-five red alerts were called in all. On nine of these alerts, hostile aircraft were known to be in the area, although only three of them attempted attacks. Alerts were kept at a minimum to avoid delay in unloading the ships.
Alerts and warnings of approaching flights, both hostile and friendly, were called tot he Fleet over TBS by the naval air officer, whose position was next to the senior controller where he could overlook the operations table. All air information was available to him, and he in turn could keep the senior controller advised of all pertinent naval information. Through his familiarity with the ship, its officers, and the flag officers, he gave advice and help in many problems which arise when Army and Navy work together.
Stand-by for fighter direction
Since the USS Catoctin was second stand-by director, all information concerning the status of defensive patrols was kept current on the patrol status board. All operational channels were manned and monitored by controllers sitting in front of the operations table, where the complete air picture was always displayed. Thus fighter direction could have been taken over without disruption of control. In fact, on several occasions control of certain channels was actually taken over while the FDT was temporarily off the air on these channels.
At 1400 on D plus 4, the control of Tac/R and fighter-bomber missions was turned over to XII TAC Advance ashore. At 1200 on D plus 7, control of fighter patrols was turned over to the 64th Fighter Wing SOR ashore by FDT #13, and the USS Catoctin ceased to be a stand-by.
Simultaneously the responsibility for air raid warning was also assumed by the 64th Fighter Wing ashore. The rebroadcasting of these warnings to ships in the harbor was made the duty of the Combat Information Center of the USS Catoctin.
It is of interest that, even though the USS Catoctin could have handled fighter direction as well as fighter-bomber and Tac/R control in an emergency, it was evident to all concerned that the separation of these activities was beneficial to the smooth working of the plan. The mobility of a separate fighter direction ship and the value of the possible additional equipment must be recognized.
On several occasions there were more transportation targets than there were aircraft to take them, for the following reasons:
Bad weather at base prevented missions from arriving in the assault area as scheduled.
Carrier-based aircraft, although in close proximity, were all out on other missions or otherwise unavailable.
The speed of the advance made the distance involved too great to employ patrols which came up with bombs for transportation targets. Their fuel would have been inadequate for both the mission and the patrol.
FILTER
Air opposition was very light and at no time afforded a fair test of the air defense system. From D-day through D plus 6, the following tracks appeared on the filter table:
Total number of tracks 1,538 Total hostile tracks 9 Total unidentified tracks 503 Total made hostile 2 Total made friendly 203 Total remaining unidentified 298 Total friendly tracks 1,231
Planes of two fighter groups assigned to XII TAC for this operation did not carry IFF equipment and were frequently plotted as unidentified tracks, which caused unnecessary alarm and alerting of the Fleet. On every occasion that hostile planes were known to be in the area, some indication of their presence was passed by the Radio Intercept Team. Information reached the filter table from: Radar (USS Catoctin), Naval Radar Guard, FDT #13 Track Broadcast, Ground Control Intercept Reporting, Ops #2 Ashore Track Broadcast.
There were sufficient radar and reporting facilities, but land echoes caused by the rugged terrain often made it impossible to obtain continuous tracks and at times even to detect targets. One GCI, the FDT #13, and two or three Navy ships were the effective radar sources during the initial phase of the operation. Ample radio channels were allotted to make the radar reporting system. Although the effectiveness of the channels varied from time to time, there were always enough usable channels for reporting. If the channels became unsatisfactory as the assault progressed, information was passed over prearranged stand-by channels, which worked very well. There were three main reporting nets.
Naval Radar Guard net
There were 16 ships in this net, of which four were appointed guard ships and four were stand-bys, the others being ready if called upon. The FDT #13 passed unidentified and hostile tracks over this channel when difficulty was experienced on the track broadcast channel.
Ground Control Intercept Reporting
Four GCI stations were scheduled to report on three VHF channels and one HF channel. Only two receivers and one transmitter were available for the three VHF channels, so the receivers were changed from time to time among them to get the best radio reception and information. There was too little traffic to demand separate VHF channels for each GCI. Indeed, better liaison could have been maintained if all the GCI stations had been on the same channel. The station scheduled to report on HF channel had difficulty getting set up ashore. When it did, contact was not good, so that the less satisfactory W/T had to be used in place of R/T.
Track Broadcast
Due probably to an unfortunate allocation of frequencies rather than to poor radio discipline, a number of stations blocked the HF track broadcast channel, rendering it useless much of the time. In one 5-minute period, nine station calls were heard, some in French, that did not belong on this frequency. After the FDT #13 began to call tracks over the FM and VHF frequencies, this channel was no longer necessary and was secured.
As has been said, the FDT #13 was the fighter control ship, its duty to control defensive patrols over the beaches and to broadcast all unidentified and hostile tracks. An air-sea rescue team with high speed launches was attached to the ship. For lack of space in the control room they operated from the visual platform topside. However, since the controllers were in constant contact with the aircraft and had a better over-all picture of the situation, they usually handled the operational matter themselves.
The FDT #13 was a British-manned, converted LST with a mixture of U.S. and British equipment. The radar equipment consisted of a CGI and Type 11, the presentation of which could be remoted to the air control room. The VHF transmitters and receivers were BC-639 and BC-640 with RM 26-A control boxes. However, the toggle switches were disconnected and press-to-talk handsets were used, which proved better. The ship had no SG radar or surface search radar capable of picking up low-flying aircraft. Had this equipment been at hand, the one night attack experienced might have been detected in time. Fortunately no damage resulted.
Daytime control was handled primarily by 64th Fighter Wing personnel. The number of aircraft on the four patrols varied from 28 to 32. However, after D-day the schedule was not adhered to and at times there was a shortage of aircraft. Night fighter activity was handled by British personnel, with one U.S. controller on duty to handle all other matters. There were four to six night fighters on patrol, and some of these were handed over to the various GCI stations whenever conditions permitted.
An AAA liaison officer on the ship maintained radio communication with his batteries ashore. Information on hostile raids and friendly flights was passed by him to his shore batteries, which in turn gave him any information they had. In a few cases where our own night fighters entered the Inner Artillery Zone they were fired upon. Except at dusk, when identification was difficult, the control of AAA was good, and no friendly aircraft was shot down.
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It is obvious that a decided change has taken place in the tactics used by the AAF in amphibious operations since the summer and autumn of 1943.
In the invasion of southern France, fewer than 30 fighter aircraft on an average were kept over the assault area for protection of the Fleet and the beaches. This is in contrast to the 60 to 80 aircraft protecting the landings at Salerno, a smaller operation in a smaller area.
The answer lies in the tremendous air supremacy the Allies built up in that year through effective offensive air warfare. Thus, offensive air warfare was conducted from the USS Catoctin, in contrast to defensive air warfare controlled from headquarters ships in previous operations.
The excellent cooperation and coordination among the several services and forces involved, along with the ample facilities of the joint operations room, made a success of the Air Command Post Afloat.
