U boats were not quite the submarines we have come to expect from WW2, in 1914 they were submersible double hulled torpedo boats, about 64 metres in length, equipped with four torpedo tubes, armed with a deck gun and crewed by about 35 officers and men. The ability to change density with compressed air between their two hulls allowed them to float or sink. Their ability to attack like a torpedo boat without returning to base was the major asset. While underwater it could move deeper or return to the surface by the use of hydroplanes, which also adjusted the trim. More ships were taken by threatening with the deck gun than sunk by torpedoes. Torpedoes were always the last option. SM U35 was the most successful U-boat during WW1, sinking 224 ships, 195 of them under a single commander Lothar de la Perière.

Life on board the U boat during a cruise was most uncomfortable – the two shifts hot bedded – that is each crew member shared his bunk with a member of the other shift. The use of the periscope when submerged was a mixed blessing, it was the ‘eye’ of the captain and crew but it also revealed the position of the U boat. The only weapons available against submarines in 1914 were the gun or to ram. These were dependent on the submarine surfacing.

Minefields were not a strength of the British war effort, in 1914 the mines were old and had poor triggering mechanisms. By 1917 a more efficient ‘horned’ mine, copied from a German model, was available. In 1915 an attempt to mine the Heligoland Bight was initiated to prevent U boats entering the North Sea. This minefield was largely ineffective as mines broke loose and floating mines alerted U boat commanders. By 1917 a Northern Barrage was being planned, this would be a minefield across the North Sea between Scotland and Norway. The US navy were keen on this plan and helped lay the minefield. Whether this second minefield was worth the effort is debatable, U boats continued to move through the area with the loss of about six boats. Nets were used when possible, some had small charges attached to them which would explode when submarines came into contact with them. Depth charges were in their infancy in 1914 – barrel shaped bombs which were dropped off the stern of the destroyer when the officer thought the submarine was directly below them. By 1916, a combination of depth charges, with sensors to detonate at determined depths, and hydrophones to listen for the presence of a submarine were used to some success.

By 1915 a new smaller type of U boat was constructed for operation off the Flanders coast. These were the UB boats. They were 28 metres long and were equipped with two torpedo tubes and a deck machine gun. Only 20 of these coastal boats were built and were operated with a crew of about 14 officers and men. These were the submarines in the pens at Ostend and at Zeebrugge that the 3rd Ypres campaign in 1917 was devised to capture and neutralise.

Also, in 1915 a minelaying U boat was designed, these were called UC coastal submarines. 15 were built and started laying mines in 1916. They were 33 m in length, and were equipped with six internal mine tubes in place of torpedo tubes. The crew was 14 men, the same as UB boats.

In 1916 two merchant submarines, known as Deutschland boats, were constructed to avoid the blockade and trade with sympathetic firms in the United States, trading chemicals and gems for rubber and minerals. They could carry 700 tons of cargo and had a crew of 29 men. They were not armed and therefore not warships. Only one made successful journeys across the Atlantic, the other was lost with all hands on its maiden voyage. After the USA entered the war, the remaining Deutschland boats were converted into conventional armed submarines.

Within the overall strategy of the German armed services, the German Navy waged a ‘klienkrieg’ (little war) against the Royal Navy. Realising that a head-on battle was unlikely to be won by the German Navy, the aim was to reduce the size of the British fleet, hopefully reducing the number of capital ships, by the use of mines, torpedo boats and submarines. The base for these operations was to be the Ostend-Zeebrugge-Bruges triangle. By the end of September 1914, U boats had sunk three British cruisers. After these initial successes, attention was turned to commerce raiding – reducing the British ability to transfer anything by sea. This was an Economic War. The British retaliated by establishing a blockade on trade bound for Germany. Neutral mercantile ships were stopped and searched when encountered.

By 1915, U boats were taking their toll on merchant shipping to the extent that new defences had to be considered. Depth charges were still in their infancy and unless a U boat could be lured to the surface, it was unlikely that a successful encounter could be achieved. It was with this in mind that Q-ships were used. Named after their home port, Queenstown in Ireland, these were armed merchant ships crewed by the Royal Navy. After luring the U boat to the surface, the hidden guns could then be used to sink the U boat. After several successes came the Baralong Incident. HMS Baralong was a Q ship operating in the Southwest Approaches. Having lured U27 to the surface while it was attacking another merchant ship, gunfire from the Baralong forced the U boat crew to abandon ship. The German crew made for the other merchant ship whereupon the Baralong’s captain ordered the machine guns to be turned on the Germans. No one survived. The neutral merchant ship’s crew told their story once they reached port and the German government accused the Baralong of committing an atrocity. In all, the Navy converted over 100 merchant ships into Q ships which were used to mixed success until the end of the war.

Unrestricted submarine warfare in 1917 had two repercussions – the entry of USA into the war as an ally of Britain and the instigation of the convoy system. After the sinking of the Lusitania in 1915, American opinion against Germany and pro-Allied feeling increased. President Wilson’s government declared war on Germany on April 6th. The convoy system had been opposed by the Royal Navy as it was feared it would involve too many naval ships, depriving the battleships of the fleet from essential support. It was the appointment of Eric Geddes to the admiralty and the forced retirement of Admiral Jellicoe that led to the acceptance that convoys were essential for survival.

In April 1918, the U boat bases at Ostend and Zeebrugge were attacked. Attempts were made to block the channels but these were cleared in two days.

Ultimately the U boat campaign failed, the convoy system kept England supplied and the war ended with the November Armistice in 1918. In total 373 German U boats were constructed of which 178 were lost by enemy action

Report by Peter Palmer