sentences:  A successful blockade of these bases would force German submarines to operate out of more distant ports, such as Wilhelmshaven, on the German coast.This would expose them for longer to Allied countermeasures and reduce the time they could spend raiding.The ports of Ostend and Zeebrugge (partially blocked in the Zeebrugge Raid three weeks previously) provided sea access via canals for the major inland port of Bruges.