Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Secretary of the Navy Josephus Daniels
TELEGRAM. No. 171
From Admiralty Date 1 July.17.
To B.Naval Attaché Washington 2050
<For>: Secretary of the Navy
Number sixtyseven. It is absolutely essential that notification be given as far in advance as possible preferably three to four weeks in advance of prospective movements of troop or other government convoy requiring escort of our destroyers (stop) If this is not done plans here for escort of merchant convoys may be fatally interfered with (stop) As merchant and troop convoys approach on widely separate routes and as escorting destroyers are not available for both at same time it is essential that plans be coordinated in advance (stop) It is practically certain that the enemy knew position of the first rendezvous and accordingly sent a submarine to intercept before juncture with destroyers (stop) It is probable that they learned this by interception of messages sent in unsafe codes (stop) It is therefore earnestly recommended that all vitally important messages be sent in British Admiralty codes (stop) This isolated instance should not influence Department to extend rendezvous farther westward owing limitation of oil and radius and time absent from other vital duty.
Source Note: Cy, UK-KeNA, Adm. 137/656. Date “1.7.17” handwritten at the bottom of the page.