During the first year of the war there was nothing to suggest that Britain, the world's main carrier, would experience a shipping shortage of critical proportions. But by the end of 1915 the cumulative effect of factors associated with the enlarged scale of the conflict had begun to strain merchant shipping. In the first place, British merchant ships were requisitioned to transport troops, animals and stores to the various theaters of war. As many continental ports were closed to British traffic, it became necessary to travel longer distances to fetch food and raw materials. To make matters worse, much of Britain's overseas imports went to supply the requirements of its allies who were cut off from their prewar sources – Italy from countries now at war with it, and France from its own provinces now held by the enemy. Then, too, the submarine menace had not only reduced available tonnage, but required ships to take circuitous routes to avoid the danger zones. Finally, ships were often immobilized for long periods owing to congestion in the ports.

As the months passed, the exigencies of the war required increased imported supplies, while the number of ships to transport them diminished. In January 1916 the Asquith government appointed a Shipping Control Committee under Curzon to advise on allocating the requisitioned tonnage with the essential needs of the country.