1915 February 10 President Wilson warns Germany that the U.S. will hold it "to a strict accountability" for "property damaged or lives lost." German submarine warfare is taking a heavy toll on neutral shipping, including American.

U-boat captains are in a difficult position because they cannot safely surface to allow enemy crews to board liferafts before being sunk. The fragile U-boats themselves are easily sunk by small-caliber deck guns.