During both World Wars, the island of Britain was dependent upon huge numbers of merchant ships to bring in food and essential raw materials, and protecting this lifeline was one of the highest priorities for British forces. If this lifeline could be severed, the British Empire in Europe would have to either sue for peace; negotiate an armistice; or abandon the British Isles as a base of operations to blockade the sea approaches to Western Europe; giving Germany in effect, complete mastery of Western Europe, with no tactical base in Europe to oppose that control.