. Unlimited submarine warfare is a type of naval warfare in which submarines sink merchant ships without warning, as opposed to attacks per prize rules

. The Germans used their U-Boats to disrupt the movement of merchant marines

. Germany had over 30 U-Boats patrolling the waters of Europe

. Most of the time, they would destroy cargo ships, claiming they had military supplies on them

. Most famous sprinkling by the U-Boats was the Lusitania

Unlimited Submarine Warfare