To counter Attack the German submarines , the Allies moved Motion shipping into convoys guarded Defending by destroyers , blockades Besieging such as the Dover Barrage and minefields were laid , and aircraft patrols Patrolling monitored Scrutiny the U-boat bases .

The French made Action numerous efforts to supply Supply their colonies during this period , attempting to use Using fast frigates to bring Bringing food and military Military_operation stores to the Caribbean past the British blockades , themselves a response Response to Napoleon 's Continental System , but often losing Earnings_and_losses the vessels in the process .