Blackett's War (38 page)

Coastal Command agreed to place one unit, No. 502 Squadron of Whitleys, under Gordon’s mathematical direction as a test. For five months Gordon tracked the status of every aircraft in the squadron as the changes were implemented. The crux of the matter was the percentage of time each plane spent in each of four different states: flying; serviceable but not flying; being serviced; or awaiting service. As expected, the percentage of time a plane spent waiting to be serviced increased. But the increase in flying hours more than made up for it: flying hours nearly doubled.

In the process, the scientists poked into everything from inspection schedules to the time spent waiting for spare parts to arrive to the rate at which various components of an aircraft fail. One of their interesting discoveries was that for a large class of components, routine inspections were literally a waste of time: a part like a fuse or a spark plug lead was “just as likely to go wrong at one moment as the next” and inspections revealed little or nothing. In fact, when they started plotting the failure rates of various parts, they found that inspections in many cases
increased
breakdowns, apparently the result of disturbing components that had been working fine. The results produced by the rationalization of maintenance procedures and flying schedules in 502 Squadron were another of those operational research contributions that spoke for themselves. Joubert ordered the policy instituted throughout the command—and asked the ORS scientists to take charge of implementing it.
³¹

The mathematician T. E. Easterfield, who joined the group later that year and was promptly grabbed by Gordon to help with the work, found that the general attitude among the aircrews was that the scientists “might be mad, but they got results.” Easterfield thought the scientists were viewed as “licensed jesters” whose odd behavior was tolerated because they served a purpose. Gordon’s one-track mind and tenaciousness were madder than most; but so, too, his results were commensurately greater than most. “Marvelously efficient chap!” remarked one RAF officer to Easterfield about Gordon—before adding, “But he was no gentleman!” To the RAF aircrews,
Gordon was known as Joad, a nickname they bestowed on him after C. E. M. Joad, the eccentric and discussion-monopolizing resident philosopher on the popular BBC radio talk show
The Brains Trust
.
³²

WILLIAMS AND BLACKETT WERE
meanwhile working on another approach to tighten the noose around the U-boats. Since 1941 air patrols had been regularly flying over the Bay of Biscay, the roughly 300-mile-by-300-mile bottleneck that all of the U-boats had to transit between the French ports and their stations on the mid-Atlantic convoy lanes. Williams calculated that in the second half of 1941 every U-boat that put to sea on a patrol had a 30 to 35 percent chance of being attacked by Allied aircraft during either its outward or inward passage of the bay.
³³
In response, the Germans had taken to transiting the bay submerged during daylight hours, surfacing at night to recharge their batteries.

Most of the Coastal Command aircraft by this point were equipped with 1.5-meter-wavelength ASV Mark II radar sets, but the results had been disappointing. The aerials for the radars were an ungainly sight, mounted on a row of four pylons perched along the spine of the planes’ fuselages. The radar’s detection range was not much better than what the naked eye could achieve by day. At night, the problem turned out to be not how far the radars could see ahead, but rather their
minimum
range. The powerful radio pulse sent out by the transmitter would instantly fry the circuitry of the sensitive receiver located right next to it, so the receiver was automatically switched off for a fraction of a second as each pulse went out. But this meant the system was unable to detect echoes bouncing off very close objects, which would arrive back at the receiver during the hundred thousandth of a second or so while it was still switched off. In practice, anything closer than three quarters of a mile was invisible. If the sea was choppy, waves on the surface would add a clutter of echoes that extended out even farther. The ASV planes could thus pick up on their radar screens surfaced U-boats at night at a range of as much as ten to twenty miles, but as they approached they would lose the radar contact at a point where the boat was still well beyond the range the eye could see at night; there was no way to follow through with the actual attack.
³⁴

One way to bridge the gap between the minimum radar range and the point of attack was to equip the patrol planes with powerful searchlights that could be switched on for the final attack run. The first of these needed
their own Ford V-8 engine and 35-kilowatt generator, or a bank of batteries completely filling the bomb bay, to supply the required electricity. An inventive RAF officer assigned to Coastal Command headquarters, Squadron Leader Humphrey de Verd Leigh, came up with the idea for a more efficient carbon arc lamp that would need only seven 12-volt batteries, which could be trickle-charged from a small generator driven by one of the aircraft’s engines. The whole package weighed less than 600 pounds.
³⁵

In a February 1942 paper, Williams had calculated that a balanced day and night force with 50 Leigh Light–equipped aircraft and an additional 100 long-range Catalinas or Liberators could increase the chances of intercepting each U-boat on its inward or outward passage to well over 50 percent.
³⁶
He was also able to provide a reassuring calculation proving that the Germans had not yet taken the step of countering the Allied radar by equipping the U-boats with warning receivers that could pick up a radar signal, which would give them time to dive before the would-be attacker came within striking distance. The poor success of No. 502 Squadron that same month when it tried to carry out night radar attacks using dropped flares to illuminate the target area made some Coastal Command officers worry that the Germans already had deployed such a threat-warning receiver. But Williams showed that the number of sightings by day per flying hour for ASV and non-ASV equipped aircraft were still roughly the same.
³⁷

By June 1942 the first Leigh Light–equipped planes were operating and the number of nighttime attacks shot upward.
³⁸
Again, the operational researchers were able to produce convincing calculations showing that the sighting rate was very close to the theoretical values expected, assuming the Germans still had not deployed a radar warning device.

The impact on German morale was instantaneous. The security of the night had been shattered: Dönitz ordered his boats to reverse procedure and return to surfacing by day, the idea being it would be a more even fight in daylight when the U-boat crews could visually spot an approaching airplane and possibly have time to submerge. By July the average number of U-boats at sea reached seventy and the return to the convoy attacks was keeping the tonnage total at a steady half million or so a month.
³⁹
But it was a much tougher and grimmer fight than ever. On July 27, Dönitz made a radio broadcast to the German people unlike anything they had ever heard from a high official of the Third Reich. He told his listeners that the “harsh realities of submarine warfare” meant Germany must expect sacrifice and losses. Dönitz later explained that he was worried by the exaggerated hopes
of easy victory that had been raised by a torrent of official propaganda and felt that a dose of caution was needed to prepare the public that, as he said in his broadcast, “even more difficult times lie ahead of us.”
⁴⁰
It was, thought the British Admiralty, a clear indication that Dönitz was planning to pour even more of his force into the convoy battle.

In September he issued new orders emphasizing that the war was now a fight for survival. The immediate impetus for the orders was a chaotic incident in which the British troopship
Laconia
, carrying 1,800 Italian prisoners of war from North Africa along with some British soldiers and women and children, was torpedoed 500 miles north of Ascension Island by
U-156
. The German submarine assisted the survivors, taking nearly 200 on board and towing four lifeboats while radioing a message that it would not attack any Allied vessel that came to assist. Dönitz approved, and requested Vichy French ships from West Africa to help in the rescue of the British passengers and Italian prisoners. Two days later an American B-24 from Ascension Island spotted the surfaced U-boat, and attacked. The German captain immediately ordered his passengers onto the lifeboats, cut them loose, and escaped serious damage by diving, but one of the lifeboats filled with Italian POWs was sunk. A few hours later the Vichy French ships arrived and picked up the remaining survivors.

It was a confused incident and it was unclear how much of Dönitz’s humanitarian concerns were prompted by the consideration that one of his captains had torpedoed a ship full of Axis prisoners. But it became the pretext for his order of September 17 that was the final culmination of the progressive brutalization of the war at sea:

At some point that fall Dönitz issued another order, which was formally reiterated the following year in a war diary entry that referred to this earlier directive, calling the attention of his U-boat commanders to the usefulness of torpedoing the rescue ships attached to convoys. “In view of the desired annihilation of ships’ crews,” Dönitz stated, “their sinking is of great value.”
⁴²

The increased Allied air activity over the bay had given Dönitz a moment of uncharacteristic doubt about whether the war could be won at all. He noted in his war diary that “the numerical strengthening of enemy flights, the appearance of a wide variety of aircraft types equipped with an excellent location device against U-boats have made U-boat operations in the eastern Atlantic more difficult.” He went so far as to admit that if the situation in the bay continued, it might lead to “a decline in the prospects of success of the U-boat war as a whole.”
⁴³
The pressure eased in late September with the arrival of the countermeasure the British scientists had long anticipated, a radar search receiver that could be used by the U-boats while transiting the bay. The German electronics industry had largely been commandeered by Göring’s Luftwaffe to produce radios and other equipment for aircraft and had no spare capacity to develop or manufacture new devices for the navy, but Dönitz at last was able to find two French companies to do the work. The Metox receiver (named after one of the French firms) could detect the 1.5-meter signals from the British ASV Mark II radars at a range of over thirty miles. That was farther than the radar system could detect a surfaced U-boat. The first sets were rather crude, consisting of a wooden-framed cross-shaped aerial that had to be lashed to the conning tower and removed before the boat could dive. The crews dubbed it the Biskaykreuz—the Cross of Biscay. Once again the U-boats could make the perilous passage on the surface by night with little fear of being caught without warning. In October, Coastal Command’s ASV squadrons detected only a single U-boat at night for the entire month.
⁴⁴

Despite that temporary setback, the experiment in bringing the fight to the enemy in the bay had yielded a wealth of data on which to lay future plans for a more decisive operation. In Costal Command ORS Report No. 204, “Air Offensive Against U-boats in Transit,” issued on October 11, 1942, Williams was able to calculate precisely how much flying time was required to sink a U-boat in the bay. He also was able to forecast, with what would prove to be remarkable prescience, the sequence of tactical and technological countermeasures that were likely to ensue as the war progressed.
And because by this point the chances of sighting a U-boat under any set of given circumstances could be calculated “with considerable accuracy,” as Blackett would note, it would be possible to get almost instantaneous warning if the Germans shifted tactics or introduced a new technological countermeasure, just by monitoring the sighting rates attained by sub-hunting aircraft.
⁴⁵
Regardless of the inevitable evolution of gadgets and tricks, the methods that Blackett and Williams had largely been responsible for developing and perfecting would keep the Allies abreast of them. In any case, the current advantage that the Metox receiver had given the U-boats in the bay would only last until Allied aircraft equipped with the new centimeter-wavelength radar arrived. The first of those were expected within months.

THE TEMPO AND INTENSITY
of the thrusts and counterthrusts in the Battle of the Atlantic was matched by developments in the cryptographic shadow war throughout that fraught summer and fall of 1942. The B-dienst’s success against the Allied Naval Cypher No. 3 had played a major part in Dönitz’s decision to rejoin the convoy battle in the summer of 1942.
⁴⁶
Key to making the wolf pack tactics work was knowing where the convoys would be ahead of time. Meanwhile, Bletchley’s blackout in reading the Atlantic U-boat Enigma signals continued.

GC&CS’s breakthrough the previous summer in the naval Enigma had been the British code breakers’ one remaining ace in the hole in negotiations with their American counterparts. While offering to share the intelligence results they extracted from the German naval signals, Bletchley insisted on keeping control of the actual code-breaking process. The British had also evaded repeated requests from the U.S. Navy for blueprints of the bombes. Partly, it was a matter of ongoing British doubts about whether the Americans could be trusted to keep a secret. More important, however, was the Admiralty’s keen awareness that whoever controlled the information could control how it was used operationally. Knowledge really was power in this case. But Britain’s leverage was rapidly slipping: you could hardly call the game if you were out of chips. Everyone who was working on the problem recognized that the ultimate solution was to build a four-rotor version of the bombes: these could apply the same proven method that worked before (and which was still working to break daily traffic of the three-rotor Enigmas used on German air force and army networks) to crack the four-rotor Enigmas now employed on the Atlantic U-boat network.