The most significant effect U-boats had on fighting land was the shortage of supplies they caused by eliminating merchant ships during the First and Second World Wars.
U boats were the English term used to refer to the German "U-Boot" or "Unterseeboot" which were submarines developed by the Germans during the First and Second World Wars. Although U boats were used in combat by targeting enemy battleships, their main use was to exercise naval blockades, as the engaged their attacks on merchant ships from the Allies who brought supplies to the United Kingdom and the Soviet Union.
