These German maps highlight the widespread and numerous attacks launched by Germany's U-boats throughout the war. By November 1918, Germany had sunk more than 5,000 merchant ships and more than 100 warships; tens of thousands of lives were lost. This was achieved at a high cost to the German navy, as 217 of its 351 submarines were sunk with a loss of more than 5,000 sailors. The German effort, nonetheless, could not overcome Allied sea power and their industrial capacity to replace lost ships and supplies. The map of the restricted zones depicts areas where Germany threatened to sink both Allied and neutral merchant ships and shows cross-sections and detailed plans of a German U-boat.