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This article is excerpted from a forthcoming book on the effectiveness of submarine operations during the 20th Century.

During World War I German U-boat operations were focused initially on sinking enemy warships. Later they became involved in mercantile warfare, that is attacking shipping carrying war material to Great Britain. Established rules and regulations came into play and hampered submarines with their low freeboard, small crews, and inherent vulnerability. The German Navy and government, facing in their view a merciless British blockade designed to starve Germany into submission, cast off adherence to the Rules of Civilized Warfare, and commenced an unprecedented unrestricted submarine warfare campaign against Great Britain, its allies and any neutral nations engaging in maritime trade with Great Britain. However there were also some little known submarine special operations conducted by the German U·boat Service, and they are the subject of this article.

During the First World War strategic communications used two modes of transmission: underwater telegraph cable and long range radio. Great Britain, France, Germany and a few other countries had invested in underwater cables but Great Britain led the world in the number of cables it controlled. The British government well understood the importance of strategic communications and the advantages that such control could bring them. Plans had been formulated to attack German cables in the event of war. The desired result would be to force German cable traffic to flow through British controlled cables, where the messages could be intercepted and read, or to force the traffic into radio transmission mode where it could be intercepted. British plans were to impose an information blockade on Germany in parallel with the economic shipping blockade it envisioned if a war occurred.

This story begins with British attacks on German undersea cables using surface ships, and the inevitable German countermoves, but segues into little known German special operations using submerged U-boats to attack British and Allied cables.’ In 1911 in Great Britain a Special Subcommittee of the Committee of Imperial Defense considered the role of undersea cables in strategic communications in the event of war. Plans were made to sever enemy cables at the start of war. The General Post Office, which controlled cable laying and repair operations, and the Royal Navy, agreed to cut five major German cables in the English Channel. The British army was tasked with plans to defend cable landing sites against enemy raiding parties that might come ashore to destroy British cable facilities. 2 The Eastern Telegraph group agreed to stockpile cable supplies and cable repair ships at appropriate locations within the Empire.

For Great Britain the First World War began on 4 August 1914 when Germany invaded neutral Belgium, in violation of treaty, and refused a British demand to withdraw its forces. The British Empire immediately set its operations into gear to sever German cable connections. On the second day of the war, British civilian cable ship ALERT left the port of Dover and sailed into the English Channel. When it reached the appropriate location it dragged for and pulled up five German undersea telegraph cables to her deck and cut them.3 This severed many of Germany’s cable links to its colonies in Africa and other locations, and forced German authorities to send a great deal of message traffic from their high powered radio station at Nauen, near Berlin. Such traffic was subject to interception and could possibly be deciphered.

That day, S August 1914, the Joint Naval and Military Committee, a Special Wartime Subcommittee of the Committee of Imperial Defense, met to consider further action against German communications with her overseas colonies. Prior to the war mainland Germany and her colonies in Africa and the Pacific were connected by cable and radio, and it was feared that those communications would be used to direct German naval units against British seaborne trade. Personnel from the Foreign Office, the Colonial Office and military representatives attended. In addition to the Channel cables that had already been cut, the Joint Committee directed attacks on German radio stations in her African colonies and the destruction of the German-controlled cable facilities at Yap Island in the Pacific:’ On 12 August HMS TRIUMPH destroyed the Yap Island cable facility with naval gunfire. Operations to capture or destroy radio stations in West and East African colonies were begun. Later that year, in November, the Royal Navy cut another German cable near the Azores which carried traffic from Tenerife to Monrovia in Liberia. The following year, on September, 1915 the British cable ship TRANSMITTER cut the German cable to Brazil, off Monrovia.

The German government also understood the importance of strategic communications, and had planned to sever its enemies’ cables in the event of war. In the Baltic the Germans attacked the Great Northern Company cables that linked Russia with its allies, France and Great Britain. Later, between September 29 and November 30, German warships attacked the cable connecting Denmark with Russia at the ports of Libau and St. Petersburg. In the Black Sea German battleship GOEBEN cut the cable between Sevastopol and Varna, Bulgaria. Russia was now without direct cable links to Great Britain and her principal ally- France. Since Russian and French military operations were supposed to be coordinated against the common foe Germany, that situation presented a serious problem.

In the Pacific area, German cruisers attacked British cable stations on small islands to destroy terminal equipment and cut the cables on shore. But before long German cruiser squadrons had departed the Pacific and this threat ended. In the Atlantic, British naval superiority limited German surface force activities to the Baltic Sea and close-in operations in the North Sea.

Since British naval superiority prevented ordinary hostile surface ship operations against British and allied cables, the German Navy turned to its submarine arm which had demonstrated a capability to operate all around the British Isles.

In 1915 German U-boats began submerged attacks on cables in the North Sea and Adriatic at depths of 40 fathoms or less (240 feet). The submerged U-boat trailed a grapnel, attached to a wire rope, and trolled in the approximate position of the cable until the grapnel caught (on something). Cable locations were no secret but navigation out of sight of land had a fairly large area of uncertainty in the days before GPS. The wire rope was attached to one of two motor-driven winches driven by the capstan and controlled from inside the U-boat. An engineer monitored a strain gage attached to the wire rope. Increased tension indicated that something had been snagged. The grapnel apparatus contained a shearing mechanism and if everything went well, the U-boat was able to snag and cut the cable. The U-boat operated at slow speed on the battery about I 0 to 20 feet above the sea bed while carrying out this operation.

Training operations were carried out in Germany, near the port of Emden on the North Sea. The mechanism used may have been a Lucas cutting and holding grapple. Germany operated cable ships of her own and her engineers would have been very familiar with the technology involved.

U-47 distinguished itself in the northern Adriatic Sea by accidentally cutting an Austo-Hungarian cable while conducting training operations near Pola in Austria, a major naval base.7 Since the Germans and the Austro-Hungarians were allies, there had to have been some embarrassment. How do you say “Oops” in German?

U-47 distinguished itself in the northern Adriatic Sea by accidentally cutting an Austo-Hungarian cable while conducting training operations near Pola in Austria, a major naval base.7 Since the Germans and the Austro-Hungarians were allies, there had to have been some embarrassment. How do you say “Oops” in German?

To reach cables beyond the North Sea required the use of specially outfitted and trained long range submarines. The German Admiralty proposed the use of U-cruisers (U-151 through 157). They were large (65 meters in length, and 1,875 tons submerged displacement) with a range of 25,000 miles at 6 knots. They were designed and built in 1916-1917 to be commercial submarines to import critical goods through the British naval blockade. DEUTSCHLAND made two successful round trips to the United States in 1916. BREMEN was lost early in 1917 on her first voyage, possible due to a mine. They were unarmed.

Six more cargo submarines were still under construction. They, along with DEUTSCHLAND, were converted into U-cruisers, long range submarines, equipped with torpedo tubes and two 105 mm. guns. DEUTSCHLAND became U-155.

The German High Seas Fleet staff objected to the Admiralty scheme on the grounds that cable attack operations were too difficult technologically and that the diversion of the U-cruisers would interfere with the ongoing unrestricted submarine campaign that commenced on 1 February 1917. The Admiralty won the argument, not unexpectedly, and the U-cruisers were equipped, trained, and detailed to cable cutting duties in addition to attacks on Allied merchant ships.

From 10 to 12 February 1917, U-155 cut British cables between the British Isles, Portugal, Gibraltar, and the Azores. After the United States entered the war in April 1917, the German Admiralty identified cables off the U.S. coast as possible targets.

During the period March- April 1918 four cables were attacked off the Iberian and African coasts. Three U-cruisers damaged cables to the Mediterranean, Africa and America at points off Lisbon, and Sierra Leone in West Africa.

On March 7- 8, U-155 attacked cables off the Spanish coast. In April U-153 and U-154 attacked cables off West Africa. Room 40 of British naval intelligence intercepted and deciphered a radio message setting up a rendezvous on 11 May between U-153 and U-154. Two British submarines, J 1 and E 35 were sent to the rendezvous area to ambush the German boats. E 35 was submerged and sighted U-154 on the surface, and made a submerged approach. She missed her with one torpedo which was not seen by the target’s lookouts and sank her with two more torpedoes. U153, in the vicinity and operating on the surface, saw the explosion and sighted E 35 on the surface briefly. E 35 then re-submerged and moved away before U-153 could avenge her comrade.

On 28 May 1918, U-151 succeeded in severing two cables off New York City. In June 1918 the British Admiralty complained that six different cruiser U-boats had attacked cables off the Azores, Lisbon, Gibraltar, Dakar, Freetown, and off the United States. In mid-September 1918 British cables off Portugal were attacked.

However all was not peaches and cream for the U-cruisers. It was difficult for the U-boat to know if it had severed a cable, merely damaged it, or at worst had just moved it a short distance along the sea bottom. In one instance U-157 had to abort her cable operations off the Azores when she lost both grapnels. U-156 was probably lost to a mine in September 1918 while returning to base through the North Sea Mine Barrage.

The British undersea cable infrastructure was too strong to fold under what were essentially pin prick attacks. The author of Nexus opines that an attack on the vital and scarce British cable ships might have been more productive. However, the British Admiralty was well aware of their value and vulnerability while lying to, conducting cable repair operations, and regularly assigned escorts to them.

In early 1918 the U.S. Army was faced with an increasing volume of cable traffic to France to support the American Expeditionary Force in France. Laying additional cables would take far too long, so other means to increase capacity were examined. One idea looked feasible. If messages were not enciphered, more information could be pushed through the cable per time unit. The Army Chief Signal Officer was not completely comfortable with that proposal, although it was commonly believed that underwater cable traffic was not capable of being intercepted. He contracted with AT&T to test that assumption. AT&T, in connection with Western Union and Western Electric, pulled up an operating cable to Europe from the sea bed, placed an induction sleeve around the cable, and discovered that they could read the cable traffic without the cable operators on shore having any indication of their eavesdropping. The neat assumption died, and the Army continued to encipher its traffic.

Some may have read the book, Blind Man’s Bluff, about the use of U.S. submarines in clandestine operations against the Soviet Union during the Cold War. The authors reported that USS HALIBUT (SSN 587) entered the Sea of Okhotsk and used an induction pod to read and record important Soviet cable message traffic between their commands on the Kamchatka Peninsula and headquarters further west. 10 I believe that the official U.S. Navy comment about Blind Man’s Bluff, published in 1998, was “no comment”. It is fascinating to realize that the same basic technology reportedly used by HALIBUT was developed in 1918 to test the vulnerability of cable traffic from the United States to France.

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