WWI Battle - Unrestricted submarine warfare

Unrestricted submarine warfare

A.    Tactics

1. Germany wanted to block trade in Britain because trade was essential to a nation, especially in times of war.

a.       Germany understood that by restricting Britain’s trade, Britain would be weakened because she would lose resources to support its war effort.

2. The German declared warzone of 1915 included the English Channel and waters surrounding the United Kingdom.

a.       This declaration allowed Germany to initiate a commerce war with Britain’s trade partner, thereby restricting Britain’s trade.

3. German U-Boats were built larger and sturdier than British submarines.

a.       This allowed U-Boats to undertake individual operations and made them ideal for launching torpedoes to surface ships.

4. Initially U-Boat activity in 1915 was contained within the Mediterranean to avoid sinking American ships.

a.       This allowed Germans to block trade to Britain without aggravating the US and prompting them to join the war.

5. The British developed antisubmarine vessels to combat the U-Boat campaign.

a.       One example is the Q-boat, which were disguised merchant vessels used to lure U-Boats. They were responsible for about 10% of U-Boats sunk.

6. The use of the “depth charge”, beginning in 1916, was the Allies’ main antisubmarine measure.

a.       These underwater bombs were responsible for sinking 27 U-Boats –more than any other anti-sub tactic. It was effective because depth charges were hard to detect since they were deep in the water, and hard to avoid because they were planted deeper than submarines and subs could not attack downwards.

7. Saturation depth charging increased after June 1917

a.       Saturation depth charging made the waters extremely dangerous for U-Boats. This was the main reason for the fall in German morale for the U-Boat Campaign following 1917.

8. More than 90% of U-Boat victims were independent targets.

a.       Therefore the British employed the convoy system in mid-1917.  The success of U-Boat attacks significantly declined and shipping losses fell to 148 ships per month (compared to 242 in early 1917).

9. Allied ships used chain link netting as an antisubmarine tactic.

a.       They were positioned around the mouth of harbours/ports to stop submarines from entering.

b.      They were hung from the side of warships to stop torpedoes. 

B.     Events

1. In early 1915 Germany declared a war zone where all Allied trade ships would be sunk.

2. In March 1917 Germany declared unrestricted submarine warfare.

a.       Indiscriminate action of the Germans completely changed nature of naval warfare –the livelihood of neutral nations was affected. This caused their sympathies to shift to the Allies.

3. In May 1917 German U-Boats sunk the Lusitania. There were 128 American casualties.

a.       The event was pivotal in turning the American public’s opinion against Germany, which significantly contributed to American entry into the war.

C.     Outcomes

1. 396 British and neutral ships were torpedoed in 1915.

2. 507 001 tons of British shipping was lost to German U-Boats in March 1917.

a.       Such a large degree of loss for one month exemplified the effectiveness of the U-Boat Campaign in restricting British trade.

3. The first half of the German campaign was sinking 242 Allied ships per month.

4. By 1917 the British had to employ rationing to its citizens.

a.       The U-Boat campaign was truly affecting civilian life, worsening their living conditions and their morale.

5. US entered the war on the Allied side in April 1917.

a.       This was prompted by German attacks on US ships through unrestricted submarine warfare.

D.    Lessons Learned

Charles Townshend. The Oxford History of Modern Warfare. 2005.          
“Firepower replaced manpower as the instrument of victory.”

Winston Churchill, First Lord of the Admiralty said “it would have been possible for Admiral Jellicoe to lose the war in an afternoon.” (Admiral Jellicoe was the commander of the British Fleet)

Alfred Thayer Mahan. The Influence of Sea Power Upon History. 1890.

A nation can be powerful “Only by military command of the sea by prolonged control of the strategic centers of commerce… and such control can be wrung from a powerful navy...”