The Allied Naval Conference, held in London September 4th and 5th, which Mayo attended, took up not only the barrage project, but another proposition our Navy Department had suggested months before, a close offensive in German waters. After the meeting Mayo cabled:
Conference completed after agreement upon the following points:
1. That close offensive in German waters should be carefully considered by Allies, after which they should indicate to British Admiralty contribution of old war ships they are prepared to furnish should offensive prove practicable.
2. That alternative offensive employing effective mine field or mine net barrage to completely shut in North Sea not practicable until adequate supply satisfactory type mines assured, and that pending such supply, extension present system mine fields desirable and that mine net barrage impracticable.
This indicated to us that the British still doubted the effectiveness of a barrage, as well as our ability to furnish an adequate supply of mines. It was evident that, after five months of earnest advocacy, further urging was needed to secure approval of the project. Benson, therefore, on September 12th, cabled Mayo:
There are great possibilities in the satisfactory solution of the mine and depth-charge question. Officers sent over here most satisfactory and remarkably well posted. I think it would help the whole situation wonderfully if Commodore Gaunt could visit the Admiralty for a few days and have a heart-to-heart talk. No time to be lost.
What happened next? The day after Benson's message was received, the British Admiralty made out for Mayo a paper entitled, "General Future Policy, Including Mine Policy," with an appendix, "Mine Barrage Across the North Sea." The policy outlined by the Admiralty, announced September 14th, was the same the Navy Department had suggested nearly five months previous.
Even then there was delay. On October 9th, Sims reported that the Admiralty was "thoroughly investigating the question" and that "the discussion of this question will probably be postponed by the Admiralty until the return of the commander-in-chief." We were still not certain as to whether the British were ready to put it through. But, believing that the plan must finally be put into effect, our Bureau of Ordnance went ahead, and let the contracts for 100,000 mines. Upon Mayo's return October 15th, the amendments suggested by the British were approved by the General Board and accepted by the Department. Nothing definite, however, had come from London and on October 20th Sims was cabled:
The Department requests to be informed whether the plan for the placing of a mine barrier across the North Sea on the Aberdeen-Egersund line has the approval of the Admiralty.
Finally on October 22nd, an answer direct from the British Admiralty said, "Admiralty has approved mine barrier and now confirms approval."