By early October 1939, the bulk of the Wehrmacht and Luftwaffe had redeployed from Poland to attack France. Hitler made a final appeal to the British and French to call off the war, but to no avail. He then ordered the Germans to launch the offensive against France, but the German generals were not ready and the action had to be postponed. The delays went on week after week until, finally, the coldest winter in memory set in and the offensive had to be put off until spring. The interval of inaction was called the “Phony War” or Sitzkrieg or Drôle de guerre.
During that fall Admiral Raeder urged Hitler to seize neutral Norway by political subversion or military force. His reasons were several. The Kriegsmarine believed that the British and French planned to occupy Norway to shut off the winter flow of high-grade iron ore from Narvik to Germany and to gain bases from which to launch air attacks on Germany and Kriegsmarine forces and bases in the Baltic Sea. There was also a possibility that Germany’s erstwhile ally, the Soviet Union, which had ruthlessly invaded Finland, might overrun all of Scandinavia, dangerously flanking Germany to the north. A German occupation of Norway would not only defeat those possibilities but also gain naval bases for the Kriegsmarine outside the North Sea, from which even the short-legged ducks could reach British shipping lanes.
Hitler grasped the strategic advantages of this proposal. He therefore commenced an attempt to subvert the Norwegian government through a Norwegian traitor, Vidkun Quisling. At the same time he directed his military chiefs to draw plans for taking Norway—and Denmark as well—by force, should subversion fail. The Kriegsmarine was to play the dominant role in the conquest, employing all the power it could muster, including every available U-boat. In the revised grand strategy, the conquest of Norway and Denmark was to precede the attack on France by about a month.
Pending the launching of these enterprises, Karl Dönitz, promoted to rear admiral, was to continue the U-boat war against Great Britain and France. In planning operations for the fall and winter of 1939-1940, Dönitz was beset by three major problems.
The overriding problem was the acute shortage of oceangoing U-boats.
Although Raeder and Hitler had canceled the Z Plan, work continued on numerous surface ships: the two super-battleships Bismarck and Tirpitz; an aircraft carrier, Graf Zeppelin; three heavy cruisers, Prinz Eugen, Lützow, and Seydlitz (being converted to an aircraft carrier); and scads of destroyers, motor torpedo boats, minelayers, and minesweepers. As one consequence, it was not possible to initiate action to speed the completion of the U-boats under construction. During the first six months of the war, September 1939 to March 1940, only six new oceangoing boats were to be commissioned: three VIIBs, one IX, and two improved models of the latter, designated IXB. If the September loss rate (two oceangoing boats) continued, by March 1940 there was to be a net loss of six oceangoing boats, down from twenty-seven to twenty-one.
Moreover, the hard Atlantic patrolling and combat had uncovered some severe design flaws and weaknesses in the existing oceangoing boats. The engine casings of the Type VIIs were not strong enough. All the VIIs had to go into the shipyards for new engines. The engine-exhaust valves on the VIIs, which closed against (rather than with) sea pressure, leaked dangerously at deep depths, a flaw that had not been discovered earlier owing to the OKM’s order to limit peacetime diving to 150 feet. Until these (and other) flaws were corrected, the nine surviving boats of the Salzwedel Flotilla, comprising one-third of the Atlantic force, were unsafe for combat. Owing to the jam-up in the shipyards, the flaws could not be immediately corrected. In the interim, those boats could only be used sparingly.
To bolster the Atlantic force, Dönitz was compelled to resort to two fairly desperate measures. First, he made the decision to continue patrolling with the two big experimental boats, U-25 and U-26, regardless of the risks entailed. Second, he confiscated a big U-cruiser, Batiray, which Krupp was completing for Turkey. However, before this boat (designated U-A) could safely patrol the Atlantic, it had to have extensive modifications in the shipyards.
The second problem confronting Dönitz was the spreading belief that the submarine torpedoes were defective.
This was not an easy matter to prove. Torpedoes and torpedo pistols were very complicated. The line officers of the Kriegsmarine commanding U-boats, as well as Dönitz and his staffers, were not trained engineers or scientists. Few had even attended a college. They had to rely on the experts at the Torpedo Directorate for technical judgments. At first the experts insisted, not without some justification, that most of the reported torpedo failures, malfunctions, and misses were the fault of poor torpedo maintenance and mistakes in shooting by green captains and crews.
From the beginning of this disputation, Dönitz took the position that while some failures and misses were doubtless the fault of the crews, not all could be so attributed. No less than thirteen skippers had reported erratic or malfunctioning torpedoes while on patrol in September. These included the analytical-minded Otto Kretschmer in the duck U-23, who had achieved a nearly perfect shooting score in peacetime, but had unaccountably missed a slow-moving tramp steamer off northeast Scotland with four torpedoes. Two skippers, Glattes in U-27 and Schuhart in U-29, had experienced and reported dangerous “premature” explosions with magnetic pistols after runs of less than 300 yards.*
After compiling a detailed and damning analysis of the torpedo performance by the September boats, Dönitz persuaded Raeder and the OKM to order the Torpedo Directorate to conduct an exhaustive technical investigation. Almost immediately the Directorate conceded two flaws that might be adversely affecting the’ magnetic pistols: a poorly designed cable layout in the electrics, and some kind of mechanical flaw, not yet isolated, in the air torpedoes. The Directorate recommended a rearrangement of the cables in the electrics, which was certain to cure the problem in those, but pending further investigation, the skippers should use only contact (or impact) pistols in the air torpedoes.
Dönitz had deepest misgivings about the results of this “investigation.” He and many of his skippers—including Otto Kretschmer—believed the main problem was that the torpedoes were running deeper than set. The Directorate had not even addressed this possibility. Nonetheless, Dönitz had no choice but to rely on the technicians. Accordingly, he issued the advisories and new instructions for the boats preparing to sail in October.
The third major problem besetting Dönitz during the winter of 1939-1940 was a continuous demand from Raeder and the OKM to provide U-boats for special missions.
From the earliest days of hostilities, Raeder and the OKM intended to foul British seaports with magnetic mines. The main planting was to be carried out by destroyers, which were to dash across the North Sea and back in winter under cover of darkness. But the destroyers could only reach the lower east coast ports of the British Isles. Those ports beyond reach of the destroyers—in the western English Channel, the west coast of the British Isles, and the northeast coast of Scotland—were to be mined by aircraft and submarine. In addition, Raeder intended to employ submarines to mine the British naval base at Gibraltar and, provided Hitler approved, the port of Halifax, Nova Scotia, where the convoys from North America formed up.
When presented with this elaborate submarine mining plan, Dönitz objected. If carried to its fullest, the plan would require the diversion of virtually every available combat-ready U-boat. Dönitz believed it was imperative to continue the torpedo war against shipping for its psychological impact, to hone the skills of the skippers and crews under combat conditions, and to continue the elusive hunt for the torpedo defects. Besides that, many skippers and crews were not qualified in minelaying.
The upshot was a compromise. During the new-moon periods of the winter months, when nights were black and long and thus ideal for minelaying, Dönitz was to employ about one-third of the oceangoing U-boat force to lay about fourteen minefields in the west coast ports of the British Isles and Gibraltar. The North Sea ducks were to lay about a dozen fields in east coast and English Channel ports, backstopping the destroyers and aircraft.
In addition to these mining missions, Raeder and the OKM proposed other special tasks for the oceangoing submarines. Dönitz deflected most of these proposals, but Berlin insisted on three. The first was to send several boats into the Mediterranean Sea to attack Allied shipping. The second was to send several boats to the Arctic, where they were to secretly base in Murmansk and prey on Allied shipping engaged in transporting timber (for mine props) from Scandinavia to Great Britain. The third was to land Abwehr(German intelligence) spies in neutral Ireland, who were to inflame anti-British sentiments.
The shortage of combat-capable oceangoing boats, the infuriating and inexcusable torpedo defects, and the demand for boats to carry out special missions significantly reduced the ability of the U-boat arm to inflict any serious damage on Allied maritime assets during the winter of 1939-1940. Nonetheless, Dönitz and his loyal, dedicated submariners were determined to give their utmost.