An exhilarating breakdown of some of history's most decisive battles. With expert analysis and eyewitness accounts examining the strategy behind the chaos of the war. From the start of the First World War in 1914, Germany pursued a highly effective U-boat campaign against merchant shipping. This campaign intensified over the course of the war and almost succeeded in bringing Britain to its knees in 1917. On 4 February 1915, Germany declared a war zone around Britain, within which merchant ships were sunk without warning. This 'unrestricted submarine warfare' angered neutral countries, especially the United States. After failing to seize control of the sea from the British at the Battle of Jutland in 1916, Germany resumed unrestricted submarine warfare on February 1st, 1917. On April 23rd, 1918, British naval forces attacked U-boat bases at Ostend and Zeebrugge. By the Armistice, the U-boat threat had been neutralised.