German U-boats, short for "Unterseeboot," were submarines used by the German Navy during both World Wars. They played a crucial role in naval warfare, particularly in disrupting supply lines by targeting merchant ships. U-boats were designed for stealth and could operate underwater for extended periods, making them formidable opponents. During World War I and World War II, U-boats employed tactics like unrestricted submarine warfare, which aimed to sink enemy vessels without warning. Their effectiveness led to significant losses for the Allies, prompting the development of countermeasures such as depth charges and convoy systems to protect shipping routes.