Indeed, this is putting the figure high; and, of course, we suffered losses.

The French and Italians were not producing any vessels of this type, whilst the Japanese were, in the early part of 1917, not able to spare any for work in European waters, although later in the year they lent twelve destroyers, which gave valuable assistance in the Mediterranean.

The United States of America were not then in the war.

Consequently measures for the defence of the Allied trade against the new menace depended on our own production.
Our _submarines_ were being produced at an average rate of about two per month only, and--apart from motor launches, which were only of use in the finest weather and near the coast--the only other vessels suitable for anti-submarine work that were building at the time, besides some sloops and P-boats, were trawlers, which, whilst useful for protection patrol, were too slow for most of the escort work or for offensive duties.

The Germans' estimate of their own submarine production was about twelve per month, although this figure was never realized, the average being nearer eight.