While the naval staff within the Admiralty handled the bulk of material and information regarding the war at sea, the War Cabinet provided a forum for regular political oversight of the conduct of the maritime campaign. The War Cabinet also allowed the Admiralty to share information, both good and bad, and raise interdepartmental problems.
The main concern of the war at sea was the threat posed by the German attack on Allied merchant shipping. Of all the different ways to attack trade - mines, submarine and surface raider - submarine attack was the most dangerous. At the same time, brief routine reports of shipping losses and naval actions were presented to the War Cabinet on almost a daily basis.
Between December 1916 and February 1917 U-boats and mines laid by German submarines were stopping and sinking merchant vessels under the 'Prize' or 'Cruiser' rules. The submarine menace was the main problem faced by the British in these months.
Countermeasures to deal with the submarine problem were regularly discussed, with the defensive arming of merchant vessels particularly provoking discussion at Cabinet level. Discussion focused on the impact the early winter of 1917 would have on the supply of guns to the British army.
The problem of the submarine-laid-mine also attracted interest. With the German declaration of unrestricted submarine warfare on 31 January 1917, the submarine menace became an even graver issue for the Cabinet. The First Sea Lord (or his representative) now gave regular briefings on the amount of merchant shipping lost to submarines.
It became clear that existing anti-submarine measures were ineffective and that mercantile losses were increasing. In order to release ships for the campaign against the U-boats, abandoning military operations in Salonika was even considered.