d arrive at this
rendezvous as an organized unit, well practised in station-keeping by
day, and at night, with the ships darkened, and that the vessels should
be capable also of zigzagging together and of carrying out such
necessary movements as alterations of course, etc.; otherwise the convoy
could not be safely escorted through the danger area. (b) The other
essential was the presence of the escorting flotilla in sufficient
strength.

It has been mentioned that there was an insufficient number of vessels
available for use as convoying cruisers. It was estimated that about
fifty cruisers or armed merchant ships would be required for this
service if the homeward-bound trade to the British Isles alone was
considered. An additional twelve vessels would be necessary to deal with
the outward-bound trade. At the time only eighteen vessels were
available, and these could only be obtained by denuding the North
Atlantic entirely of cruisers.

The situation in regard to destroyers or other fast vessels presented
equal difficulties. Early in February, 1917, we had available for
general convoy or patrol work only fourteen destroyers stationed at
Devonport and twelve sloops at Queenstown, and owing to repairs and the
necessity of resting officers and men periodically, only a proportion of
these were available at any one time. A number of these vessels were
required to escort troop transports through the submarine danger zone.
During the month of February six sloops were diverted from their proper
work of minesweeping in the North Sea and added to the patrol force at
Queenstown, and eight destroyers were taken from the Grand Fleet and
sent to southern waters for patrol and escort duty. There were obvious
objections to this weakening of the North Sea forces, but it was
necessary in the circumstances to ignore them.

This total of forty destroyers and sloops represented the whole
available force at the end of February. Simultaneously a careful
investigation showed that for the institution of a system of convoy and
escort for homeward-bound Atlantic trade alone to the United Kingdom,
our requirements would be eighty-one destroyers or sloops and
forty-eight trawlers (the latter vessels being only suitable for
escorting the slow 6-7-knot ships of the trade from Gibraltar to the
United Kingdom). For the outward Atlantic trade from the United Kingdom
our estimated requirements were forty-four additional destroyers or
sloops.

The de