What promoted Germany to use boats and unrestricted submarine warfare?

Germany resorted to unrestricted submarine warfare primarily to counter the British naval blockade, which severely limited its access to vital supplies and resources during World War I. By targeting not only military vessels but also merchant ships, Germany aimed to disrupt Allied supply lines and weaken their war effort. This strategy was intended to bring a swift end to the conflict, but it ultimately led to heightened tensions with neutral countries, particularly the United States, contributing to America's entry into the war.