In the case of a convoy encountering a minefield, as in the case of a fleet, several ships may be sunk practically simultaneously.
During the year 1916, whilst I was still in command of the Grand Fleet, suggestions as to convoys had been forwarded to the Admiralty for the better protection of the ocean trade against attack by surface vessels; but it was pointed out to me that the number of cruisers available for escort work was entirely insufficient, and that, consequently, the suggestions could not be adopted.

This objection was one that could only be overcome by removing some of the faster merchant ships from the trade routes and arming them.

To this course there was the objection that we were already--that is before the intensive campaign began--very short of shipping.
Shortly after my taking up the post of First Sea Lord at the Admiralty, at the end of 1916, the question was discussed once more.

At that time the danger of attack by enemy raiders on shipping in the North Atlantic was small; the protection needed was against attack by submarines, and the dangerous area commenced some 300-400 miles from the British Islands.

It was known that unrestricted submarine warfare was about to commence, and that this would mean that shipping would usually be subjected to torpedo attack from submarines when in a submerged condition.