Part of the Allied plan for the invasion of mainland Europe called for the capture of port facilities, in order to ensure the timely delivery of the enormous amount of war material required to supply the invading Allied forces (it was estimated that the 37 Allied divisions to be on the continent by September 1944 would need 26,000 tons of supplies each day). The main port the Allied forces hoped to seize and put into their service was Brest, in northwestern France.