10 Facts About Submarine Warfare in World War One

World War One is often referred to as the ‘first modern war’ – and in the war at sea, many tactics and much technology was in use for the first time at scale. Effective submarine warfare was a particularly new phenomenon, with Germany focusing on U-Boat production to counter the larger British surface fleet and put pressure on its Atlantic supplies. Below are 10 facts about this new form of warfare:

1. HMS Pathfinder was the first ship sunk by a U-Boat

On 5 September 1914 Royal Navy ship HMS Pathfinder was sunk by a torpedo from a German submarine at the Firth of Fourth. Casualty figures for the attack are disputed but by one estimate only 18 of 268 people on board survived.

This attack came as a shock to Royal Navy commanders who had been divided over whether it was possible to sink a large surface vessel using a submarine.

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2. 12,850,815 tons of shipping was sunk by U-Boats

Although their exact policy varied throughout the war the German U-boats racked up a total of 12,850,815 tons of shipping sunk. The highest total for a single year was 1917, when unlimited submarine warfare resumed and 6,235,878 tons was sunk.

3. 178 U-Boats sank in combat

Submarine U-14, sunk near Peterhead on 5 June 1915 but lost only one crew member.

This represented 50% of Germany’s total U-boat capacity and resulted in the deaths of around 5,000 members of U-Boat crew.

4. German U-Boat numbers more than quadrupled 1914-1918

Newly constructed U-Boats docked at Kiel.

In 1914 Germany had 29 U-Boats at its disposal by the time they surrendered in 1918 the fleet comprised 134.

5. The greatest loss of life in a single sinking was 1,926

On 8 June 1916 SS Principe Umberto was transporting Italy’s 55th infantry regiment back from Albania to Italy. Despite being under escort by other ships the Austo-Hungarian sumbarine U-5 was able to torpedo the Principe Umberto and it sank rapidly killing 1,926.

6. The RMS Lusitania sank in only 18 minutes

Ships attacked by torpedo tended to sink rapidly hence the high casualty rates. The passenger ship Lusitania was torpedoed on 7 May 1915 and within 18 minutes its bow touched the sea bed. The sinking killed 1,198 of those aboard, leaving 761 survivors.

7. Submarines inflicted more damage than surface craft

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Submarines quickly became the most prolific killers in the Fleet of the German Empire. In 1914 surface ships sank 55 ships against only 3 sunk by U-Boats. The following year this was reversed and Submarines sank 396 Allied ships compared to only 23 by surface craft.

The greatest disparity came with the resumption of unlimited submarine warfare in 1917 when 2,439 Allied ships were sunk by U-Boats against 64 in conventional naval battles.

8. The largest submarine was the U-155

SM U-155 was exhibited in London after the war before being scrapped in 1921.

The U-151 class of submarines were 315 feet long and could carry 700 tons of cargo. They traveled at around 12 knots and had originally been designed as merchant submarines under the name Deutschland.

9. U-Boats provoked both the USA and Brazil into war

Brazilian President Venceslau Brás signs the declaration of war on the Central Powers.

Although there were obviously other factors at work the USA and Brazil both cited the German attacks on civilian and merchant vessels as key provocations in bringing them into the war.

10. Unrestricted submarine warfare was seen as a war crime

The court building in Leipzig which held the post-war war crimes trials. It still serves as the German Federal Court today.

The Unrestricted submarine warfare of World War One was regarded by many at the time as a kind of war crime as it violated Prize Rules, naval codes common since the 19th century which stipulated that merchant vessels could not be attacked without warning.

Prize Rules also featured in the 1907 Hague Conventions which were an early attempt to lay do laws for war crimes and the conduct of war.

Commander Karl Neumann was tried at Leipzig in 1921 for sinking the hospital ship Dover Castle in the war but was acquitted as he did so under orders. These apprehensions were abandoned by World War Two and all nations engaged in unrestricted submarine warfare leading to huge numbers of non-combatant deaths at sea.