The War at Sea and Gallipoli » The U-Boat Threat and the Lusitania

The U-boat threat

In the lesson The War in the North Sea: Raids, Dogger Bank and Jutland you saw that Germany's big ships could not break the British blockade. Germany's answer was the U-boat, its name for a submarine. On 22 September 1914 a single U-boat, U-9, sank three old British cruisers in about an hour, and more than 1,400 sailors died.

The greater danger was to trade. Britain bought much of its food and raw materials from abroad, and they all came by merchant ship. If U-boats sank enough of those ships, Britain could be starved into making peace.

Under the accepted rules of war at sea, often called prize rules, a warship had to stop a merchant ship and let the crew get into the lifeboats before sinking it. For a U-boat this was very risky. On the surface it was slow and thin-skinned, and a merchant ship could ram it. So on 4 February 1915 Germany declared the seas around the British Isles a war zone. From 18 February, Allied merchant ships there could be sunk without warning, and neutral ships sailed at their own risk. This is called unrestricted submarine warfare.

Key terms:

• U-boat: a German submarine (from the German word Unterseeboot, 'undersea boat')
• Merchant ship: a ship carrying goods or passengers, not a warship
• Prize rules: the rules of war at sea that said a merchant ship must be stopped and its crew allowed to leave before it was sunk
• Unrestricted submarine warfare: sinking merchant ships without warning, whatever country they came from
• Neutral: not taking part in the war

The sinking of the Lusitania, 7 May 1915

The Lusitania was a huge British passenger liner owned by the Cunard company. On 1 May 1915 it left New York for Liverpool. That morning the German Embassy had placed a notice in American newspapers, warning travellers that British ships in the war zone could be destroyed. Few passengers took it seriously.

On 7 May, off the south coast of Ireland, the submarine U-20 fired one torpedo into the liner without warning. A second explosion followed inside the ship, and it sank in about 18 minutes. Of nearly 2,000 people on board, 1,198 died. They included 128 Americans.

Opinion in the USA turned sharply against Germany. After another British liner, the Arabic, was sunk in August 1915, Germany backed down. In September 1915 it called off its unrestricted campaign around Britain, because it feared bringing the USA into the war.

Unrestricted submarine warfare returns, 1917

By the end of 1916 the blockade was causing hunger in Germany, and the fighting on land was stuck. The German navy offered a way out. It worked out that if U-boats sank 600,000 tons of shipping a month, Britain would have to ask for peace within about five months. The USA might join the war, but Britain would be beaten before American soldiers could arrive. On 1 February 1917 Germany began unrestricted submarine warfare again.

At first the gamble seemed to be working. In April 1917 U-boats sank about 870,000 tons of Allied and neutral shipping, the worst month of the war. About one in four of the ocean-going ships leaving British ports was not coming back. In the same month the USA declared war on Germany, as you will see in the lesson The USA Enters the War.

Anti-U-boat measures

Convoys were the most important measure, for three reasons. The ocean is so large that one group of ships was almost as hard to find as a single ship, so U-boats found far fewer targets. A U-boat that did attack now had to face the escorts and their depth charges. And convoys could be steered away from danger by radio. Fewer than one in a hundred ships sailing in convoy was sunk.

The U-boat campaign failed. Germany lost 178 U-boats in the war, and Britain was never starved out. Worse for Germany, it had helped to bring the USA into the war.

Exam-style question

Source A: From the German government's reply to an American protest about the sinking of the Lusitania, signed by the German Foreign Secretary, Gottlieb von Jagow, 28 May 1915 (translated).

'According to reports at hand here, the Lusitania when she left New York undoubtedly had guns on board which were mounted under decks and masked ... on her last trip the Lusitania, as on earlier occasions, had Canadian troops and munitions on board, including no less than 5,400 cases of ammunition ... The company thereby wantonly caused the death of so many passengers.'

Source B: From the report of the official British inquiry into the loss of the Lusitania, written by Lord Mersey, a senior judge, 17 July 1915.

'... part of it [the cargo] consisted of a number of cases of cartridges (about 5,000). This ammunition was entered in the manifest ... The steamer carried no masked guns nor trained gunners, or special ammunition, nor was she transporting troops ... The whole blame for the cruel destruction of life in this catastrophe must rest solely with those who plotted and with those who committed the crime.'

(Masked means hidden. A manifest is a ship's official list of cargo. Wantonly means recklessly.)

Study Sources A and B. How far does Source A support the evidence of Source B about the sinking of the Lusitania? Explain your answer. [8 marks]