World War I casualties
The total number of military and civilian casualties in World War I were about 40 million: estimates range from 15 to 19 million deaths and about 23 million wounded military personnel, ranking it among the deadliest conflicts in human history.
Atlantic U-boat campaign of World War I
Of the 12.5 million tons of Allied shipping destroyed in World War I, over 8 million tons, two thirds of the total, had been sunk in the waters of the Atlantic war zone. Of the 178 U-boats destroyed during the war, 153 had been from the Atlantic forces, 77 from the much larger High Seas Flotillas and 76 from the much smaller Flanders force.