Right, let's get this over with. You want a rewrite of some historical account. Fine. Just don't expect me to enjoy it.

The Mid-Atlantic Gap: A Void of Silence and Steel

The Mid-Atlantic gap. A chillingly apt term, isn't it? It’s not a place you’d find on any map, not one marked with coastlines or cities. Instead, it’s a void, a geographical phantom that haunted the Battle of the Atlantic during the Second World War. Picture this: an expanse of the unforgiving Atlantic Ocean, vast and indifferent, lying just beyond the reach of land-based aircraft. The map would show it, not with lines, but with the stark, accusing arcs of aircraft range, a black halo around the known world, marking where safety ended and vulnerability began. The blue dots, chillingly, represent the ships lost, swallowed by the depths, victims of the U-boats that prowled this no-man's-land. This was the gap, a deadly sanctuary for German submarines, a testament to the limitations of aerial reconnaissance and the insatiable appetite of maritime warfare.

History: A Scramble for Supremacy

The responsibility for hunting down these underwater predators fell, rather unceremoniously, to the RAF Coastal Command when it was cobbled together in 1936. Their arsenal, however, was less than formidable. We're talking about a paltry number of aircraft, most of them decidedly short-ranged. The common sights were the Avro Anson and the Vickers Vildebeest, both practically museum pieces by the time the war actually kicked off. The shortages were so acute, they resorted to "scarecrow patrols" with Tiger Moths, which is about as effective as bringing a butter knife to a gunfight. The real priority, naturally, was given to RAF Bomber Command, who hoovered up all the best, longest-ranged aircraft. Coastal Command was left to scavenge the castoffs, like the Vickers Wellington medium bombers. These, at least, had the range for anti-submarine warfare (ASW), but they were hardly the cutting edge. The other aircraft capable of carrying the necessary ordnance, the Avro Lancaster, was Bomber Command's prized possession, a fact that apparently required clarification. Coastal Command’s motley collection of Ansons, Whitleys, and Hampdens couldn't even lug the standard 450 lb depth charge; that required the Wellingtons or the majestic Short Sunderlands.

The real jewel in Coastal Command's crown, however limited, was the Consolidated Aircraft Liberator GR.I, more commonly known as the VLR Liberator, or simply VLR. The bomber variant, the Liberator B.I, proved too fragile for the brutal bombing missions over Europe, but its extensive range and payload made it absolutely ideal for ASW. The problem? The U.S. Navy had first dibs, using them for reconnaissance in the Pacific, where their range was equally valuable, though their missions were generally considered less critical than those of Coastal Command.

These VLRs became particularly crucial when Bletchley Park couldn't crack the Kriegsmarine's Enigma codes, meaning Ultra intelligence was unavailable. Consider the case of Convoy ON 127. On September 11, 1942, as it was being savaged by U-584, a single VLR from 120 Squadron was overhead. It was a glimmer of hope in the encroaching darkness. Then came Convoy ON 131, where fifteen U-boats converged, only to be met by aircraft. Coastal Command managed to sink two of them. Protecting Convoy ON 136, the 120 Squadron VLRs struck again, sinking U-597 on October 12, 1942. Even then, the VLRs proved their mettle in conjunction with shipborne high-frequency direction finding (HF/DF). Defending Convoy SC 104 on October 16, VLRs, guided by HF/DF, repelled three shadowing U-boats. They upped their game on October 29 for Convoy HX 212, driving off five, and then seven on November 6 around Convoy SC 107. The inadequacy of air support from Newfoundland was starkly highlighted by the early interception of SC 107 and the subsequent bitter, costly battle. This grim reality finally spurred the RAF to belatedly shift more Coastal Command squadrons to the region.

The nine Liberator GR.Is of 120 Squadron, operating out of Iceland, were a significant concern for Admiral Karl Dönitz, the architect of the U-boat campaign. Their value was undeniable; after patrols were extended to cover Canada in 1942, only one ship was lost in convoy. Yet, even by mid-1942, Coastal Command only had two squadrons equipped with Liberators and B-17 Flying Fortresses. And as soon as Coastal Command showed any success against the U-boats, Sir Arthur Harris, the formidable head of Bomber Command, immediately sought to divert their precious aircraft to his own operations, targeting German cities. It was a perpetual tug-of-war for resources, a battle within a battle.

Following the mauling of Convoy SC 118, Professor Patrick Blackett, the director of the Admiralty Operational Research Section, put forth several compelling proposals. One of them was to divert VLRs from Bomber Command to Coastal Command. Despite Blackett's strong arguments, the Admiralty, the Air Ministry, Bomber Command, and even the Americans were reluctant to reduce the air offensive in the Bay of Biscay or cease bombing German bases. The number of VLR aircraft operating in the North Atlantic in February [1943] was a meager eighteen, with no substantial increase until after the crisis in March. Even the vital night air patrols, recognized as essential, didn't commence until the autumn of 1943.

Bomber Command, to their credit, didn't entirely refuse to assist against U-boats. Between January and May 1943, they flew 7,000 sorties against the U-boat pens in Lorient, Brest, and Saint-Nazaire. The cost, however, was steep: 266 aircraft and their crews. And, rather tellingly, these raids inflicted no damage on the pens themselves nor the submarines within them. Coastal Command, for context, never even reached a strength of 266 VLRs. Raids targeting German U-boat building yards yielded similarly disappointing results.

Aircraft played an indirect but crucial role by disrupting the formation of wolf packs. They limited the safe havens for U-boat attacks and, by hindering the ability of shadowing U-boats to locate and track convoys, made shipping harder to find, thus reducing losses. This also aided the convoy escorts, allowing them to engage U-boats individually rather than facing a coordinated onslaught. Despite the willingness of Royal Canadian Air Force aircraft to fly in the perpetually terrible conditions off the Grand Banks – conditions Coastal Command would never have dared—U-boats could still trail convoys from very shortly after their departure from Halifax. Without effective air-to-surface-vessel (ASV) radar, the almost perpetual fog of the Grand Banks allowed pack operations to penetrate within a couple of hundred miles of Newfoundland while aircraft patrolled uselessly above, rendering visual detection impossible.

A method for detecting surfaced submarines at night, when they were most vulnerable while recharging batteries and felt most secure, was a paramount priority for Coastal Command. ASV radar provided this. The earlier AI.II (Mark 2 Airborne Interception) radar was adapted as ASV.II (Air to Surface Vessel Mark 2) and fitted to Coastal Command aircraft. However, Coastal Command's priority for this technology ranked behind the needs of RAF Fighter Command's night fighter units. The ASV.II’s 1½-metre wavelength (actually 1.7 meters, 176 MHz) meant that a submarine was typically lost in sea return before it came within visual range, usually at around a mile (1.6 km), by which time it was already diving. The Leigh light was developed to counter this. Despite facing indifference from the Air Ministry, it entered service in June 1941 and proved remarkably successful. However, it required a large aircraft, like the Wellington or Liberator, to carry the generator for the light. Most of Coastal Command's aircraft were incapable of this, and Bomber Command was hardly inclined to relinquish anything superior. To make matters worse, the Germans developed the Metox, which could detect ASV radar pulses before the aircraft could detect a submarine, rendering it useless.

The advent of H2S, a three gigahertz-frequency (10 cm) radar, changed the game. The combination of H2S (as ASV.III) and the Leigh light proved devastating to U-boats. Yet, Harris again denied Coastal Command any allocation of H2S systems, claiming Bomber Command needed it to find targets, prioritizing it over Gee and Oboe, and arguing that Coastal Command might lose it to the Germans. Winston Churchill supported his stance. Marshal John Slessor, head of Coastal Command, countered that Bomber Command also risked losing the technology to the enemy, allowing them to develop countermeasures before Coastal Command could even deploy it. And indeed, that’s precisely what happened. The first ASV.III was fitted to a Coastal Command Wellington at Defford in December 1942. By February 1943, twelve were based at Chivenor, while a copy of H2S was lost on February 2-3 when a Stirling Pathfinder was shot down over the Netherlands, on only its second operational mission. Harris raised similar objections to supplying the American-developed 3 cm-wavelength H2X radar units to Coastal Command (which designated it ASV.IV), again securing higher priority, and again witnessing it fall into German hands, almost exactly a year later, in February 1944.

As Coastal Command had rightly predicted, the Germans captured the damaged H2S. This would have been nearly impossible from a Coastal Command aircraft downed at sea, as opposed to over land. Telefunken then produced the Rotterdam Gerät (Rotterdam Device, named for its place of capture). Coastal Command's first ASV.III-equipped patrol took place over the Bay of Biscay on March 1. The system achieved its first U-boat contact on the night of March 17, but the carrier Wellington suffered a Leigh Light malfunction, preventing the attack from being pressed home. The first successful attack using the system occurred the following night. When ASV.III was finally operational, German submariners, including Dönitz himself, began to mistakenly believe British aircraft were homing in on emissions from the Metox receiver, which no longer provided any warning. Meanwhile, German scientists were perfecting the Rotterdam Gerät into a submersible version for U-boat defense, alongside the aviation-utilized FuG 350 Naxos radar detector for night fighters, the submersible version receiving the designation FuMB 7 Naxos U. While fragile, Naxos did work. However, it entered service on the very same day that the 10 GHz-emitting H2X (which Naxos couldn't detect) became operational in Coastal Command. Naxos was replaced by the FuMB 36 Tunis in May 1944, and was supplemented by Stumpf, which today would be classified as radar absorbent material, under the codename Schornsteinfeger ("Chimneysweep").

Just prior to the TRIDENT Conference, Admiral Ernest J. King gained control of ASW aircraft from the United States Army Air Forces (USAAF), brokering a deal to trade B-24s for comparable types. This allowed Slessor to negotiate with King for the "borrowing" of one squadron. After the devastating attacks on convoy ONS 166, the number of VLRs in Newfoundland finally saw an increase. The Canadians had been persistently advocating for Liberators since the autumn of 1942, despite British doubts about the Royal Canadian Air Force's ability to employ them effectively. The RCAF, for their part, resisted the RAF taking over a role they considered their own. Squadron Leader Bulloch, commanding officer of 120 Squadron, vouched for the RCAF's capabilities. In early March 1943, the numbers in Newfoundland belatedly increased (though not enough to constitute 10 Squadron, RCAF, until May 10), while 120 Squadron's strength doubled. Even then, this only placed a total of thirty-eight VLRs over the Mid-Atlantic Gap. The arrival of the 25th Antisubmarine Wing, USAAF, with its medium-range B-24s (equipped with H2S, likely built by Canadians), made it possible to free up Coastal Command VLRs. The growth in the number of escort carriers also meant a significant increase in USAAF Fortresses and medium-range Liberators could be based in Newfoundland. The 25th Wing flew patrols over the Bay of Biscay, sinking one U-boat before being redeployed to Morocco.

The increasing availability of escort carriers dramatically reduced the peril of the Gap. After a critical juncture in March, which nearly led Churchill and the Admiralty to abandon convoys altogether, the Mid-Atlantic Gap was finally closed in May 1943, coinciding with the operational deployment of RCAF VLRs in Newfoundland. By this point, the tide had largely turned in the Battle of the Atlantic.

See Also

• Mid-Ocean Escort Force
• Mid-Ocean Meeting Point
• GIUK gap
• CAM ship
• MAC ship
• Project Habakkuk

Notes

• ^ Bowyer, Chaz. Coastal Command at War. Shepperton, Surrey, UK: Ian Allan Ltd., 1979, p. 157.
• ^ Johnson, Brian. The Secret War. London: BBC, 1978, p. 204. The United States employed a similar expedient in early 1942.
• ^ a b c d e f g h i j Ireland, Bernard. The Battle of the Atlantic. Annapolis, MD: United States Naval Institute Press, 2003, p. 70.
• ^ a b Milner, Marc. Battle of the Atlantic. St. Catharines, ON: Vanwell Publishing, 2003, p. 99.
• ^ Ireland, p. 71.
• ^ Ireland, p. 124.
• ^ Milner, Marc. North Atlantic Run: the Royal Canadian Navy and the battle for the convoys. Annapolis: United States Naval Institute Press, 1985, p. 158.
• ^ Milner, North Atlantic Run, p. 161.
• ^ Milner, North Atlantic Run, p. 171.
• ^ Milner, North Atlantic Run, p. 173.
• ^ Milner, North Atlantic Run, p. 176.
• ^ Milner, North Atlantic Run, p. 180.
• ^ Milner, North Atlantic Run, p. 188.
• ^ Milner, North Atlantic Run, p. 158.
• ^ Milner, p. 224.
• ^ Milner, North Atlantic Run, pp. 224–225.
• ^ Milner, North Atlantic Run, p. 225.
• ^ Johnson, p. 234.
• ^ John Terraine. The Right of the Line. London: Wordsworth, 1997 ed.
• ^ John Terraine. The Right of the Line. London: Wordsworth, 1997 ed., pp. 454–455.
• ^ Milner, Battle of the Atlantic, pp. 98–99.
• ^ Milner, North Atlantic Run, pp. 140–141.
• ^ Milner, North Atlantic Run, p. 140.
• ^ a b Milner, Battle of the Atlantic, p. 101.
• ^ Johnson, p. 207.
• ^ a b c d e Johnson, p. 227.
• ^ Milner, Battle of the Atlantic, p. 102.
• ^ a b Milner, Battle of the Atlantic, p. 144.
• ^ RAF History - Bomber Command 60th Anniversary Archived 6 July 2007 at the UK Government Web Archive, Campaign Diary: February 1943 Archived 21 February 2006 at the Wayback Machine. Accessed 18 July 2008.
• ^ Johnson, p. 230.
• ^ a b Ireland, p. 188.
• ^ Gordon, Don E. Electronic Warfare: Element of Strategy and Multiplier of Combat Power. New York: Pergamon Press, 1981.
• ^ Johnson, p. 231.
• ^ a b Johnson, p. 231.
• ^ Ireland, p. 140.
• ^ Ireland, p. 141.
• ^ Milner, Battle of the Atlantic, p. 143.
• ^ Milner, Battle of the Atlantic, p. 143. The same condescension was applied to the Royal Canadian Navy by the Royal Navy.
• ^ a b c Milner, Battle of the Atlantic, p. 148.
• ^ Zimmerman, David. Great Naval Battle of Ottawa. Toronto: University of Toronto Press, 1989.
• ^ Herman, Arthur. Freedom's Forge: How American Business Produced Victory in World War II, pp. 243–244. Random House, New York, NY, 2012. ISBN 978-1-4000-6964-4.
• ^ Milner, North Atlantic Run.
• ^ Milner, North Atlantic Run, p. 239.