Consequently there was a great shortage of fast small craft for escort and mercantile convoy work.  It was estimated that the escort force required for the protection of a complete system of convoy in the Mediterranean was approximately 290 vessels, the total number available being about 215.

In spite, then, of the success of Admiral Calthorpe’s work, the result was that convoys were not started in the Mediterranean until October, and they were then but inadequately protected, and losses were heavy, both from this cause and from the fact already mentioned—­that the Mediterranean is a sea which, by reason of its confined nature, is particularly suited for operations by submarines against trade.  Its narrowness at various points, such as the Straits of Gibraltar, the Malta Channel, the Straits of Messina, and the passages to the AEgean cause such convergence of trade as to make it a very simple matter for a submarine to operate with success.  Evasion by change of route is almost impossible.  Operations designed to prevent the exit of submarines from the Adriatic were difficult, because the depth of water in the Straits of Otranto militated against the adoption of effective mining and the laying of an effective net barrage.

For the above reasons the Admiralty was always very averse to the sending of a large volume of our Far Eastern trade through the Mediterranean, and strongly urged the Cape route instead; but the shortage of shipping, combined with the increased length of the Cape route, influenced the Ministry of Shipping to press strongly for the Mediterranean as opposed to the other route.  A “through” convoy from England to Port Said was started in October, and by the end of November two ships had been sunk out of the thirty-five that had been under convoy.  The return convoy; Port Said to England, was only started in December.

The losses of British merchant steamships per quarter in the Mediterranean during 1917 is shown below: 

Quarter ending June 30 69

September 30 29

October and November 28

It is impossible to close this chapter describing the convoys without mention being made of the fine work accomplished by those upon whose shoulders fell the task of organizing and working the whole system.  I cannot hope that I have succeeded in conveying to readers of this volume an adequate conception of the great and marvellously successful performance that it was or a full appreciation of what immense difficulties the staff had to contend with.  They were very completely realized by me, who saw them appear day by day and disappear under treatment.