World War I Shipping Crisis

The Allied tonnage emergency of 1917, when Germany’s unrestricted submarine campaign sank merchant ships faster than they could be replaced. April 1917 was the worst month, with about 860,000 gross tons lost, and one in four ships leaving British ports was being sunk. Britain held only weeks of grain reserves. The Admiralty, long resistant, adopted ocean convoys from May 1917 under Lloyd George’s pressure; grouping ships under escort cut sinkings sharply through the rest of the war, though the U-boat threat persisted to the 1918 armistice.