When war broke out in August 1914, the British government moved immediately to strangle the supply of raw materials and foodstuffs to Germany and its allies. This marked the beginning of the 'hunger blockade', a war of attrition that lasted beyond the Armistice and didn't end until Germany signed the Treaty of Versailles in June 1919.
Armed with contraband lists, British naval ships spent the war patrolling the North Sea, intercepting and detaining thousands of merchant ships thought to be harboring cargo bound for enemy shores. This aggressive display of maritime power aroused considerable anger in neutral countries, many of whom enjoyed strong trading links with Germany.
Tension was heightened after the North Sea was declared a British 'military area' on 3 November 1914. Despite complaints about breaches of international law, however, most neutral merchant ships agreed to put into British ports for inspection and were subsequently escorted - minus any 'illegal' cargo bound for Germany - through the British-laid minefields to their final destinations.
The blockade strategy worked effectively. As a memorandum to the War Cabinet on 1 January 1917 stated, very few supplies were reaching Germany or its allies - either through the North Sea or through other areas such as Austria's Adriatic ports, subject to a French blockade since the first month of the war.
Germany attempted to counter the crippling effects of the blockade with a new weapon that seemed capable of subverting British naval superiority: the submarine. For much of the war, German submarines were deployed only intermittently against neutral and Allied shipping. Their devastating impact was offset by the international anger that such attacks aroused.
In spite of the international uproar, starting from 1 February 1917, the German naval command adopted a policy of 'unrestricted submarine warfare'. Despite initial successes, this high-risk strategy did not work. It finally provoked the USA into entering the war against the Central Powers and its worst effects were successfully countered by the introduction of a convoy system.
Due to the 'hunger blockade', by 1915, German imports had fallen by 55% from pre-war levels. Aside from causing shortages in important raw materials such as coal and various non-ferrous metals, the blockade cut off fertilizer supplies that were vital to German agriculture.
Staple foodstuffs such as grain, potatoes, meat and dairy products became so scarce by the winter of 1916 that many people subsisted on a diet of ersatz products that ranged from so-called 'war bread' (Kriegsbrot) to powdered milk. The shortages caused looting and food riots, not only in Germany, but also in the Habsburg cities of Vienna and Budapest, where wartime privations were felt equally acutely.
The German government made strenuous attempts to alleviate the worst effects of the blockade. The Hindenburg program, introduced in December 1916, was designed to raise productivity by ordering the compulsory employment of all men between the ages of 17 and 60. A complicated system of rationing, first introduced in January 1915, aimed to ensure that at least minimum nutritional needs were met. In larger cities, 'war kitchens' provided cheap meals en masse to impoverished local citizens.
Such schemes, however, enjoyed only limited success. The average daily diet of 1,000 calories was insufficient even for small children. Disorders related to malnutrition - scurvy, tuberculosis and dysentery - were common by 1917.Official statistics attributed nearly 763,000 wartime deaths in Germany to starvation caused by the Allied blockade. This figure excluded the further 150,000 German victims of the 1918 influenza pandemic, which inevitably caused disproportionate suffering among those already weakened by malnutrition and related diseases.
Although the blockade made an important contribution to the Allied victory, many of its devastating side effects cast a long shadow over post-war German society and like the Versailles Treaty contributed to the rise of Nazism.