At the beginning of the First World War, the Austro-Hungarian Navy's U-boat fleet consisted of six largely experimental submarines of three classes.[9][Note 2] The Navy had five larger, more modern submarines (what would have been the U-7 class) under construction in Germany at the outbreak of war, but when the Navy became convinced that delivery of the U-7 boats would be impossible, they were sold to Germany in November 1914.[10][Note 3]