Rear Admiral Ralph Earle, Chief of Bureau of Ordnance to Admiral William S. Benson, Chief of Naval Operations
Bureau of Ordnance
Washington, D. C.
To: Chief of Naval Operations.
Subject: Mine barrier.
1. This Bureau has had underway for some time the operation of placing a submarine mine barrier in various enemy zones. This barrier to be effective only against undersea craft.
2. Commander Cyprian Bridge commented as follows when the details were explained to him:
A mine barrier even on such an extensive scale as the one proposed by this Bureau, to reach from Scotland to Norway might be feasible. There is no
dou reason for not attempting the planting of such a barrier except the difficulty of getting the necessary material, that is to say the necessary number of mines. When he returns to England he will discuss the question with the Admiralty and inform it of the possibility of obtaining large numbers of mines for such a project. The first question of all to be decided will be whether of not the grand strategy of war permits or requires such an undertaking. He will inform us by cable of any decision in the matter of mines.
3. The Bureau informed him that this was a subject for settlement between the British Admiralty and our Department and that if such cable were sent, it would be to the Department.
4. The capabilities of the Bureau as to the manufacture of such a barrier, using the new antenna mine, are: minimum supply of 10,000 mines a week after a start is made, which would probably take from 45 days to two months.
5. Instructions are awaited.
Source Note: DTS, DNA, RG 45, Entry 517B.