Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Secretary of the Navy Josephus Daniels
4th September, 1917.
FROM: Force Commander.
TO: Secretary of the Navy (Operations).
SUBJECT: Approach Routes to Atlantic Coast Ports.
1. It is not at all inconceivable that German submarines may operate off the main harbors of America or the Panama Canal. In addition to torpedoing ships, they might make it very embarrassing by planting mines in localities not far from our principal harbors. if mines were discovered off any of our harbors, there would result perhaps an immediate closing of the ports and allied ships bound from Europe for America would be in immediate need of information as to how to be routed to American ports to avoid danger.
2. If the subject has not already been taken up, I recommend that the Department be prepared to meet this submarine situation by having lines of approach prescribed for different harbors and by having well defined channels of entrance that will be maintained by constant sweeping, if necessary.
3. In the Allied Shipping Office, in New York, full information with charts and so forth can be obtained on how the situation is handled in European Waters.
4. There is no doubt that submarines cannot operate advantageously on our Atlantic sea-board or remain there for any great length of time, but it is quite possible that a diversion might occur and this office would be immediately flooded with enquiries from the Allied Admiralties as to what instructions they should give their ships in order to permit them to enter American ports without danger.
Wm S. Sims.
Source Note: Cy, DNA, RG 45, Entry 517. Document identification numbers: “C/J/2/1/S”