Both Britain and Germany tried to starve each other into surrendering.
The Germans did this by the use of the submarine or Unterseeboot (U boat), to sink ships crossing the Atlantic with grain from Canada and the USA, beef from Argentina and lamb from Australia and New Zealand.
At first the German U boats surfaced, warned the British cargo ships, allowed the crew and any passengers to take to the lifeboats and then sank their victim with gunfire. But British ships began to carry hidden guns to fire at the U boats and so the Germans adopted a "sink on sight" campaign from below the waves using torpedoes.
In 1915 a German U boat sank the British liner, Lusitania and a large number of US citizens were killed in the attack. There was fury in the USA and the Americans came close to declaring war. This would have so weakened Germany that they immediately called off the campaign and went back to the old approach.
In 1917 the German High Command gambled that they could win the war by using unrestricted submarine warfare before the entry of the USA could make any difference.
In February 1917 the Germans announced that unrestricted submarine warfare would be resumed and that announcement plus German plans to offer Texas to the Mexicans led to the American declaration of war on Germany in April 1917.
Food supplies to Britain were seriously damaged by this campaign and by the summer of 1917 there was only a few weeks supply of grain left in the country. To deal with this problem the government took the following steps.
Convoys - ships were now to sail in large groups which made it easier for them to be protected by warships and more dangerous for the U boats to attack them.
Rationing - To stop food prices rising and making it impossible for all but the rich to be able to buy food and to prevent food riots and even revolution the government decided to take control of the supply and consumption of food in the UK and rationing was introduced in 1917. Everyone, including the King and Queen, had a ration book and the amount you were entitled to depended on gender, the type of work you did and its importance to the war effort.
Propaganda - Government posters and short films encouraged people to be careful with food, not to eat too much and not to hoard it. For the first time being fat became a negative quality. Fat people ate too much food which was scarce and therefore they were traitors to the country and the cause.
Dig For Victory - People were encouraged to convert spare land to more productive use - farmers, landowners, householders dug up their land to produce their own vegetables and perhaps keep a few chickens and a pig and thus save valuable space on ships on the Atlantic.
Read pages 52 and 53 and answer these questions-
How did the German navy hope to defeat Britain?
How many U boats did the Germans have by 1917?
What assurances did the Kaiser receive from his naval commanders?
What foods were in short supply in Britain?
According to source C what problems did this create?
What was the best year for the U boats?
Why did sinkings fall in 1918?
Why did rationing have to be introduced?
What items were a. rationed and b. to be used with care?
What was done to increase supplies of food produced at home?
What was the convoy system?
German U Boat Warfare - Help Questions 1,2,3,4 on page 53