Like Hall and Page, Balfour had become convinced that the US would eventually be forced into the war by German intransigence. Hall’s intelligence of German intrigues in Mexico and Cuba, about which he had briefed Hardinge earlier that day, persuaded him that the time had come to take the bull by the horns. His niece and biographer, Blanche (Baffy) Dugdale, described his reaction:
‘Ever since the middle of January … a piece of information had been in the possession of the British Government, which would move, if anything could, the populations behind the Atlantic seaboard States, who still read of the European War with as much attachment as if it be raging in the moon. This was the famous telegram from Zimmermann … The method by which this information had reached the British Intelligence Service had made it impossible for some time to communicate it to the United States Government. Therefore for over a month Balfour read in his despatches from Washington of the slow awakening of the American will to war, but could do nothing to hasten the process. Till – at last – information about the Mexican plot reached London through channels which enabled the Intelligence Service to cover up the traces of how it had first been got.’
Dugdale had been close to her uncle and her comment confirms de Grey’s account that Hall had revealed the contents of the initial telegram intercepted by Room 40 to Balfour without delay, rather than waiting several days as some commentators, including Diana Preston, have alleged. She was the first and for many years the only author to imply that Room 40 had been intercepting American diplomatic traffic.
Later that day, Balfour told Hardinge: ‘I think that Captain Hall may be left to clinch this problem as he knows the ropes better than anyone.’ He was giving Hall a free hand – a testament to the degree to which the Director of Naval Intelligence had gained the confidence of one of Britain’s most experienced and distinguished statesmen. Armed with this support, Hall decided that Balfour should ask Page to visit him at the Foreign Office where he would formally give him the telegram. On the afternoon of February 23, Page called on Balfour, who presented him with the coded and uncoded versions of the telegram. Dugdale described the historic occasion: ‘Delight was unbounded in Whitehall and the Foreign Secretary himself was unusually excited. As dramatic a moment as I remember in all my life, he once said … By the ceremony of this act the British Government gave its pledge that the communication was authentic.’
Bell noted: ‘Mr. Page came back from his interview with Balfour with a translation in his hand and blood in his eye.’ The Ambassador, Loughlin, Bell and his personal secretary, Eugene Shoecraft, sat up all night engaged in the difficult task of drafting a telegram for Wilson. They had to reconcile Hall’s security requirements with the language which could persuade the President that he was dealing with a ruthless government in Berlin which would shrink from nothing that could advance their objective of subverting the United States and rendering it impotent.
At 8 am London time on the morning of Saturday February 24, Page advised the State Department that in three hours time he would be sending a cable of great importance to the President and the Secretary of State.
By the time he had finally drafted the cable to his and his staff’s satisfaction and it had been encoded, a further five hours had passed. The final message read:
London, February 24, 1917- 1 p.m.
5747 … For the President and the Secretary of State.
Balfour has handed me the text of a cipher telegram from Zimmermann, German Secretary of State for Foreign Affairs, to the German Minister to Mexico, which was sent via Washington and was relayed by Bernstorff on January 19. You can probably obtain a copy of the text relayed by Bernstorff from the cable office in Washington. The first group is the number of the telegram, 130, and the second is one of 13042, indicating the number of the code used. The last group but two is 97 556, which is Zimmermann’s signature.
I shall send you by mail a copy of the cipher text and of the decode into German and meanwhile I give you the English translation as follows: [Page inserted here the English text of the telegram.]
The receipt of this information has so greatly exercised the British Government that they have lost no time in communicating it to me to transmit to you, in order that our government may be able without delay to make such disposition as may be necessary in view of the threatened invasion of our territory.
Early in the war, the British Government obtained a copy of the German cipher code used in the above message and have made it their business to obtain copies of Bernstorff’s cipher telegrams to Mexico, among others, which are sent back to London and deciphered here. This accounts for their being able to decipher this telegram from the German Government to their representative in Mexico, and also for the delay from January 19 until now in their receiving this information. This has hitherto been a jealously guarded secret and is only divulged to you now by the British Government in view of the extraordinary circumstances and their friendly feeling toward the United States. They earnestly request that you will keep the source of your information and the British Government’s method of obtaining it profoundly secret, but they put no prohibition on the publication of Zimmermann’s telegram itself.
The copies of this and other telegrams were not obtained in Washington but were bought in Mexico.
I have thanked Balfour for the service his Government has rendered us and suggest that a private official message of thanks from our Government to him would be beneficial.
I am informed that this information has not yet been given to the Japanese Government, but I think it not unlikely that when it reaches them they may make a public statement on it in order to clear up their position regarding the United States and prove their good faith to their Allies.
Throughout that day the senior staff of the State Department eagerly awaited the arrival of Page’s cable. Lansing had taken the weekend off, leaving his Under-Secretary, Frank Polk, in charge. Polk read the document with growing amazement and anger. Realising that he could not wait for Lansing’s return, he called the White House. Within minutes, the President received him in the Oval Office. Wilson was badly shaken and Polk eventually persuaded him to take no immediate action until Lansing could brief him once he had returned on the following Tuesday, February 27. Polk went back to the State Department to research the facts Lansing would require to communicate to the President.
As the drama unfolded in Washington, Bernstorff was enduring a miserable journey back to Germany. The ejected Ambassador, his wife and his staff, 200-strong, found passage on the Danish liner, Frederik VIII, which sailed from New York on February 15. The British had granted Bernstorff safe passage on the condition that the liner should call at Halifax, Nova Scotia for a detailed search. This diversion had been instigated by the Admiralty at Hall’s request. Having studied his intercepted messages over a period of two-and-a-half years, he had developed a high regard for Bernstorff’s powers of persuasion and worried that, even at this late hour, he might be able to argue Berlin out of a confrontation with the US. In reality Bernstorff had no influence with the military rulers of Germany and their ultranationalist allies. Taking no chances, the Navy held Frederik VIII in Halifax for no less than 12 days, only authorising the liner’s departure after the telegram had safely been in the hands of the State Department for 72 hours. The Canadian customs agents were thorough: every passenger, every cabin and every piece of luggage was searched. To their fury, Bernstorff and his party were not allowed to go ashore.
Extracted from ‘Blinker’ Hall Spymaster by David Ramsay