Unrestricted Submarine Warfare
What is unrestricted submarine warfare?
Unrestricted submarine warfare was Germany’s policy of attacking any ship that tried to
get through its U-boat blockade of Great Britain. They would attack ANY ship, whether
it was military, passenger, or merchant.
Why did Germany use this policy?
Germany used this policy because it was an effective way to blockade Great Britain,
keeping supplies and other necessary items out of British hands. Also, Great Britain had
blockaded Germany with its ships, so Germany used its U-boats to blockade Great
What was the Lusitania? What happened to it? How did the United
May 1915 The Lusitania was a British passenger liner that was attacked by German U-
boats. Around 1,200 people died, 128 of which were Americans. The United States urged
Germany to give up their policy of unrestricted submarine warfare, as it attacked
innocent and neutral ships without warning.
What was the “Sussex pledge”?
May 1916 Germany agreed to stop attacking passenger ships and give crews of
merchant vessels time to escape prior to attack (basically, give merchant ships warning
they would be attacked).
Why did Germany decide to resume using this policy?
Germany thought they could defeat Great Britain before the United States had a chance
to join the war and prepare the help on the Allied side.
How did this policy cause the United States to enter the war?
This policy made it unsafe for any ship/person to travel on the waters near Great
Britain, even if they were neutral. Also, this policy made it difficult for the United States
to trade with Great Britain and France.
What was the Zimmermann Telegram? Who sent it to whom?
A telegram sent from German Foreign Minister Arthur Zimmermann to the German
ambassador in Mexico City.
What did the telegram say?
The telegram promised the Mexican government that Germany would help it recover
land from the United States if they (Mexico) would join with Germany if they went to
war with the United States. The telegram also announced that Germany was going to
resume unrestricted submarine warfare.
Who intercepted it? Why did they wait to tell the United States about
The British intercepted the telegram and didn’t tell the United States because they didn’t
want the Germans to know that they had cracked the code.
How did this telegram cause the United States to enter the war?
Germany was asking/bribing Mexico to declare war on the United States. Mexico was a
bigger threat to the United States than Germany was because it was so much closer.
Also, the telegram announced Germany was going to resume unrestricted submarine
warfare, which it had promised to stop.
What is propaganda? Who usually publishes it?
Propaganda is information designed to influence people’s opinions. The government
usually publishes it.
How did some American propaganda describe/display Germans?
Some American propaganda described the Germans as bad, barbaric, dangerous,
wicked, ape/gorilla, abuser of women, etc.
How did propaganda cause the United States to enter the war?
If the government publishes propaganda, the people only see what the government
wants them to see. If Germany received a bad reputation and that is all the Americans
saw, the Americans might start believing it to be true, causing the Americans to become
enraged at what the Germans do. Propaganda helps the government make the people
ready and willing to go to war.
What countries did America trade with during the war?
Great Britain and France.
Could the United States have continued to trade with Germany during
Technically, yes. The United States, as a neutral country, had the right to trade and do
business with any country it wanted to, on either side of the war. However, Great
Britain’s blockade caused the United States to not be able to trade with Germany.
What was the difference in American trade with the Allies? How did it
1914: $824 million 1916: $3.2 billion
What were the amounts of American loans to the Allied Powers?
1917: Allied Powers, $2.5 billion
Central Powers, $27 million
How did American trade cause the United States to enter the war?
Germany was upset that Great Britain had enforced a blockade on it, which the United
States complied with. This British blockade led Germany to its policy of unrestricted
submarine warfare, which the United States did not like. Also, the United States wanted
to continue trading with the British and if it refused to trade with British because it
blockaded Germany, it was technically taking an act of war on Great Britain.