The Type IX U-boat was designed by Nazi Germany's Kriegsmarine in 1935 and 1936 as a large ocean-going submarine for sustained operations far from the home support facilities. Type IX boats were briefly used for patrols off the eastern United States in an attempt to disrupt the stream of troops and supplies bound for Europe. The extended range came at the cost of longer dive times and decreased maneuverability, which is why the smaller Type VII was produced in greater numbers and used for the bulk of operations.
Type IXC was a further refinement of the said class with storage for an additional 43 tonnes of fuel, increasing the boat's range. This series omitted the control room periscope leaving the boats with two tower scopes.