The number of available and future German submarines was estimated regularly.
Around 370 German submarines were in service from 1914 - 1918, around 200 of them
were lost with 5132 men dead and missing.
The sinking of merchant ships was analyzed in detail. The world merchant tonnage
in July 1914 had been 48 Mio. BRT; 19 Mio. BRT of it were British : 8,587 steamer and
657 sailing vessels. More than 2,000 British merchant ships with 6.6 Mio. BRT and
over 3,000 Allied and Neutral ships with 4.4 Mio BRT were sunk by german submarines
in World War I. British human losses alone were over 13,000 killed.
Strategy and tactics to fight the German submarines were discussed on all political
and military levels : from the War Cabinett to the First Lords of the Admiralty. Finally
the introduction of the convoy-system in the first half of 1917 overcame the menace.
ADM 137/3870 - Specifications, administration and personnel of German submarines :
Jan 1915 : Estimation of available submarines and future preview, 3 pages
Jul 1915 : Estimation of available submarines and future preview, 1 page
Dec 1916 : Estimation of available submarines and future preview, 2 pages
Jun 1917 : Estimation of available submarines and future preview, 4 pages
Apr 1918 : Estimation of available submarines and future preview, 2 pages
ADM 137/3866 - Extracts from German secret instructions for war on commerce :
Submarine results, Feb 1917, signed Bauer, 26 March 1917, 2 pages
Summary of Submarine successes, Feb - May 1917, signed Michelsen, 21 July 1917, 2 pages
ADM 137/4137 - Home Waters, Ships attacked 16 - 23 March 1917 :
Alnwick Castle, 19.03.1917, 8 pages
ADM 137/3129 - British Vessels lost, Aug 1914 - Jul 1917 :
British Vessels, 3 pages
ADM 137/4814 - British Vessels lost, Aug 1917 - Nov 1918 :
British Vessels, 7 pages
ADM 137/4817 - Foreign Vessels Sunk or Damaged by the Enemy :
Allied and Neutral Ships Sunk or Damaged 1914 - 1918, 8 pages
ADM 116/3421 - Unrestricted Sumarine Warfare [ before the introduction of convoy ], original version :
Oct / Nov 1916 : no answer to the submarine problem, 6 pages
The needle in the hay stack : destroyers search submarines, 10 pages
Feb 1917 : facts of submarine warfare, 5 pages
Feb 1917 : 540.000 BRT sunk, 1 page
Mar 1917 : 575.000 BRT sunk. The situation get out of hands - defeat in sight, 3 pages
Apr 1917 : 420.000 BRT in the first two weeks - "... building up reserves of foodstuffs while the shipping still existed ...", 3 pages