The Blockade of Germany, or the Blockade of Europe, occurred from 1914 to 1919. It was a prolonged naval operation conducted by the Triple-Entente powers during and after World War I in an effort to restrict the maritime supply of goods to the Central Powers, which included Germany, Austria-Hungary and the Ottoman Empire. It is considered one of the key elements in the eventual Allied victory in the war. The German Board of Public Health in December 1918 claimed that 763,000 German civilians died from starvation and disease caused by the blockade up until the end of December 1918. An academic study done in 1928 put the death toll at 424,000. An additional 100,000 people may have died during the continuation blockade in 1919.
Both the German Empire and the United Kingdom relied heavily on imports to feed their population and supply their war industry. Imports of foodstuffs and war materiel of European belligerents came primarily from the Americas and had to be shipped across the Atlantic Ocean, thus Britain and Germany both aimed to blockade each other. The British had the Royal Navy which was superior in numbers and could operate throughout the British Empire, while the German Kaiserliche Marine surface fleet was mainly restricted to the German Bight, and used commerce raiders and unrestricted submarine warfare elsewhere.
Prior to World War I, a series of conferences were held at Whitehall in 1905–1906 concerning military cooperation with France in the event of a war with Germany. The Director of Naval Intelligence—Charles Ottley—asserted that two of the Royal Navy's functions in such a war would be the capture of German commercial shipping and the blockade of German ports. A blockade was considered useful for two reasons: it could force the enemy's fleet to fight and it could also act as an economic weapon to destroy German commerce. It was not until 1908, however, that a blockade of Germany formally appeared in the Navy's war plans and even then some officials were divided over how feasible it was. The plans remained in a state of constant change and revision until 1914, the Navy undecided over how best to operate such a blockade.
Meanwhile, Germany had made no plans to manage its wartime food supplies since, in peacetime, it was able to produce some 80% of its total consumption. Furthermore, overland imports from the Netherlands, Scandinavia, and Romania would be unaffected by any naval blockade. However, the combined issues of conscription of farm laborers, the requisition of horses, poor weather, and the diversion of nitrogen from fertilizer manufacture into military explosives, all combined to cause a considerable drop in agricultural output.
The British—with their overwhelming sea power—established a naval blockade of Germany immediately on the outbreak of war in August 1914, issuing a comprehensive list of contraband that all but prohibited American trade with the Central powers, and in early November 1914 declared the North Sea to be a war zone, with any ships entering the North Sea doing so at their own risk. The blockade was unusually restrictive in that even foodstuffs were considered "contraband of war". There were complaints about breaches of international law; however, most neutral merchant vessels agreed to dock at British ports to be inspected and then escorted—less any "illegal" cargo destined for Germany—through the British minefields to their destinations.
The Germans regarded this as an illegal attempt to starve the German people into submission and wanted to retaliate in kind. The German High Seas Fleet set out multiple times, from 1914 to 1916, to reduce the British Grand Fleet and regain access to vital imports. The sea conflicts culminated in the Battle of Jutland in 1916, restricting the German fleet to port and enforcing the blockade.
The blockade hurt American exports. Under pressure especially from commercial interests wishing to profit from wartime trade with both sides, Washington protested vigorously. Britain did not wish to antagonize the U.S. It set up a program to buy American cotton, guaranteeing the price stayed above peacetime levels and mollifying cotton traders. When American ships were stopped with contraband, the British purchased the entire cargo, and released the empty ship.
A memorandum to the British War Cabinet on 1 January 1917 stated that very few supplies were reaching Germany or its allies either via the North Sea or other areas such as Austria's Adriatic ports (which had been subject to a French blockade since 1914).
The first accounts of the effects of the blockade in English were by humanitarians, diplomats, and medical professionals. They were sympathetic to the suffering of the German people  The official German account, based on data about disease, growth of children, and mortality, judged the British harshly, calling the blockade a crime against innocent people. The first account commissioned by the Allies, written by Professor A. C. Bell and Brigadier-General Sir James E. Edmonds, hypothesized that the blockade led to revolutionary movements but concluded that, based on the evidence, "it is more than doubtful whether this is the proper explanation." Germans wanted to end the war because of the food shortage, while workers staged a revolution because of the long term theory of socialism. The revolutionaries claimed in their slogans, for example, that they were "Arbeitssklaven" (work slaves) to the monarchy. Edmonds, on the other hand, supported by Colonel Irwin L. Hunt, who was in charge of civil affairs in the American occupied zone of the Rhineland, held that food shortages were a post-armistice phenomenon caused solely by the disruptions of the German Revolution of 1918–19.
More recent studies also disagree on the severity of the blockade's impact on the affected populations at the time of the revolution and the armistice. Some hold that the blockade starved Germany and the Central Powers into defeat in 1918. Others hold that the armistice on 11 November was forced primarily by events on the Western Front, rather than any actions of the civilian population. The idea that a revolt of the home front forced a German surrender was part of the Stab-in-the-back myth. Also, Germany's largest ally Austria-Hungary had already signed an armistice on 3 November 1918, exposing Germany to an invasion from the south. On 29 September 1918 General Erich Ludendorff#Downfall told the Kaiser that the military front was going to collapse immediately.
All scholars agree that the blockade made a large contribution to the outcome of the war. By 1915, Germany's imports had already fallen by 55% from its prewar levels and the exports were 53% of what they were in 1914. Apart from leading to shortages in vital raw materials such as coal and nonferrous metals, the blockade also deprived Germany of supplies of fertiliser that were vital to agriculture. That led to staples such as grain, potatoes, meat, and dairy products becoming so scarce by the end of 1916 that many people were obliged to instead consume ersatz products including Kriegsbrot ("war bread") and powdered milk. The food shortages caused looting and riots not only in Germany but also in Vienna and Budapest. The food shortages got so bad that Austria-Hungary hijacked ships on the Danube that were meant to deliver food to Germany. Also, during the winter of 1916 to 1917, there was a failure of the potato crop, which resulted in the urban population having to subsist largely on Swedish turnips. That period became known as the Steckrübenwinter or Turnip Winter.
The German government made strong attempts to counter the effects of the blockade; the Hindenburg Programme of German economic mobilisation was launched on 31 August 1916 and designed to raise productivity by the compulsory employment of all men between the ages of 17 and 60. A complicated rationing system initially introduced in January 1915 aimed to ensure that a minimum nutritional need was met, with "war kitchens" providing cheap mass meals to impoverished civilians in larger cities. All of those schemes enjoyed only limited success, and the average daily diet of 1,000 calories was insufficient to maintain a good standard of health, resulting by 1917 in widespread disorders caused by malnutrition such as scurvy, tuberculosis and dysentery.
German official statistics estimated 763,000 civilian malnutrition and disease deaths were caused by the blockade of Germany. That figure was disputed by a subsequent academic study, which put the death toll at 424,000. The German official statistics came from a German government report published in December 1918 that estimated the blockade to be responsible for the deaths of 762,796 civilians, and the report claimed that that figure did not include deaths caused by the Spanish flu epidemic of 1918. The figures for the last six months of 1918 were estimated. Maurice Parmelle maintained that "it is very far from accurate to attribute to the blockade all of the excess deaths above pre-war mortality" and believed that the German figures were "somewhat exaggerated". The German claims were made at a time that Germany was waging a propaganda campaign to end the Allied blockade of Germany after the armistice that lasted from November 1918 until June 1919. Also in 1919, Germany raised the issue of the Allied blockade to counter charges against the German use of submarine warfare.
In 1928, a German academic study sponsored by the Carnegie Endowment for International Peace provided a thorough analysis of the German civilian deaths during the war. The study estimated 424,000 war related deaths of civilians over the age of one in Germany, not including Alsace-Lorraine, and the authors attributed the civilian deaths over the prewar level primarily to food and fuel shortages in 1917–1918. The study also estimated an additional 209,000 Spanish flu deaths in 1918 A study sponsored by the Carnegie Endowment for International Peace in 1940 estimated the German civilian death toll at over 600,000. Based on the above-mentioned German study of 1928, they maintained, "A thorough inquiry has led to the conclusion that the number of 'civilian' deaths traceable to the war was 424,000, to which number must be added about 200,000 deaths caused by the influenza epidemic". Historian and demographer Jay Winter estimated that there were 300,000 excess deaths in Germany due to the blockade, after subtracting deaths due to the influenza epidemic.
The blockade was maintained for eight months after the Armistice in November 1918, into the following year of 1919. According to the New Cambridge Modern History food imports into Germany were controlled by the Allies after the Armistice with Germany until Germany signed the Treaty of Versailles in June 1919. From January 1919 to March 1919, Germany refused to agree to the demand by the Allies that Germany surrender its merchant ships to Allied ports to transport food supplies. Germans considered the armistice a temporary cessation of the war. They feared that, if fighting broke out again, the ships would be confiscated outright. In January, hoping to buy time, the German government notified an American representative in Berlin that the shortage of food would not become critical until late spring. Facing food riots at home, German finally agreed to surrender its fleet on 14 March 1919. The Allies allowed Germany, under their supervision, to import 300,000 tons of grain and 70,000 tons of cured pork per month until August 1919.  In April this food from America arrived in Germany. The restrictions on food imports were finally lifted on 12 July 1919 after Germany signed the Treaty of Versailles.
C. Paul Vincent maintains that for the German people, these were the most devastating months of the blockade because "in the weeks and months following the armistice, Germany's deplorable state further deteriorated." Sally Marks has argued that the German accounts of a hunger blockade are a "myth," as Germany did not face the starvation level of Belgium and the regions of Poland and northern France that it occupied. At the armistice discussions in January 1919, the Allies offered to let Germany import food if it agreed to turn over its merchant fleet, a condition that Germany refused until the last armistice discussions in March. The head of the German armistice delegation, Matthias Erzberger, balked at first at giving up the merchant fleet. He feared that if Germany surrendered it, the Allies would confiscate it as reparations. Before he surrendered the fleet, he wanted guarantees that the food imports could be financed with foreign credit owed German businesses. Leaders in industry and government feared that, by taking the fleet, the Allies aimed to sever Germany from world markets. The Allies would gain an unfair competitive edge over the German steel industries, which depended on import of ore and sale to countries abroad, by charging high prices for ocean transport. In the German Republic's official mouthpiece, the Deputy State Secretary of the German Food Office Braun made known his fear that, if the Allies took the ships, the dockworkers in the ports would revolt and rekindle the Spartacist uprising that aimed to overthrow the republic. The leaders of the German Republic had to weigh these considerations against the reality that, in early 1919, rations in German cities were on average 1,500 calories per day. 
Not included in the German government's December 1918 figure of 763,000 deaths are civilian famine related deaths during 1919. A recent academic study maintains that there is no statistical data for the death toll of the period immediately following the Armistice in November 1918. Dr. Max Rubner in an April 1919 article claimed that 100,000 German civilians had died due to the continuation blockade of Germany after the armistice. In the UK a Labour Party anti-war activist Robert Smillie issued a statement in June 1919 condemning continuation of the blockade, and claiming that 100,000 German civilians had died.
The impact on childhood was assessed by Mary E. Cox using a newly-discovered dataset based on heights and weights of nearly 600,000 German schoolchildren measured between 1914 and 1924. These data indicate that children suffered severe malnutrition. Family class was a major factor, as the working-class children suffered the most but were the quickest to recover after the war. Recovery to normality was made possible by massive food aid organized by the United States and other former enemies.
Britain still controlled the sea, and Germany never again attempted a full-scale naval confrontation. Germany was thus prevented from receiving vital war supplies and foodstuffs throughout the conflict
Jutland and Trafalgar maintained Britain’s command of the oceans and the economic blockade, which was its primary strategic weapon. The Grand Fleet anchored a British economic blockade that was slowly strangling the German war effort