But each submarine was capable of sinking many merchant ships, thus necessitating the employment of a very large number of our destroyers; and therein lay the gravity of the situation, as we realized at the Admiralty early in 1917 that no effort of ours could increase the output of destroyers for at least fifteen months, the shortest time then taken to build a destroyer in this country.
And here it is interesting to compare the time occupied in the production of small craft in Great Britain and in Germany during the war.
In pre-war days we rarely built a destroyer in less than twenty-four months, although shortly before the war efforts were made to reduce the time to something like eighteen to twenty months.

Submarines occupied two years in construction.
In starting the great building programme of destroyers and submarines at the end of 1914, Lord Fisher increased very largely the number of firms engaged in constructing vessels of both types.

Hopes were held out of the construction both of destroyers and of submarines in about twelve months; but labour and other difficulties intervened, and although some firms did complete craft of both classes during 1915 in less than twelve months, by 1916 and 1917 destroyers _averaged_ about eighteen months and submarines even longer for completion.
The Germans had always built their small craft rapidly, although their heavy ships were longer in construction than our own.

Their destroyers were completed in a little over twelve months from the official date of order in pre-war days.

During the early years of the war it would seem that they maintained this figure, and they succeeded in building their smaller submarines of the U.B.and U.C.