Many of the convoy commodores had their ships sunk under them.

The country has every reason for much gratitude to those who undertook this difficult and very responsible task.
By July we had succeeded in increasing the strength of the anti-submarine convoy escorting force to thirty-three destroyers (eleven of which belonged to the United States Navy) and ten sloops, with eleven more destroyers for the screening of troop transports through the submarine zone and for the protection of the convoys eastward from the Lizard, the position in which the other screening force left them.

We had remaining twelve sloops, which, with trawlers, were engaged in protecting that considerable portion of the trade making for the south of Ireland, which we could not yet bring under convoy.

It was intended to absorb these sloops for convoy protection as soon as circumstances permitted.
At this stage it was considered that a total of thirty-three more destroyers or sloops was needed to complete the homeward convoy system.
The Admiralty was pressed to weaken yet further the Grand Fleet destroyer force in order to extend the convoy system, but did not consider such a course justified in view of the general naval situation.
In arranging the organization of the Atlantic convoy system it was necessary to take into consideration certain other important matters.
Amongst these were the following: 1.

The selection of ports of assembly and frequency of sailing.