The Cambon letter was an unpublished letter to Zionist diplomat Nahum Sokolow issued by the French government in 1917 during the First World War announcing support for the Zionist project in Palestine, then an Ottoman region with a small minority Jewish population. It read:
You were good enough to present the project to which you are devoting your efforts, which has for its object the development of Jewish colonization in Palestine.You consider that, circumstances permitting, and the independence of the Holy Places being safeguarded on the other hand, it would be a deed of justice and of reparation to assist, by the protection of the Allied Powers, in the renaissance of the Jewish nationality in that Land from which the people of Israel were exiled so many centuries ago.
The French Government, which entered this present war to defend a people wrongfully attacked, and which continues the struggle to assure the victory of right over might, can but feel sympathy for your cause, the triumph of which is bound up with that of the Allies.
I am happy to give you herewith such assurance.
It has been argued that the letter was a necessary precondition of the Balfour Declaration.
On 11 March 1916, in a telegram to the Russian and French ambassadors, Edward Grey put forward a proposal that the Allies together issue a public declaration supporting Jewish aspirations in Palestine. Verete, in his account of the developments leading up to this proposal, explains, "here is the root and source of the pro-Zionist policy of British governments until the Balfour Declaration" 
Historian Martin Kramer argues that securing the assent of Britain's French and American Allies, and of the Vatican, which controlled many Christian Holy Sites in the Land of Israel, was a necessary precondition for the Balfour Declaration.
Both British diplomat Mark Sykes and French diplomat François Georges-Picot were in Petrograd at the time advising their ambassadors in the matter of securing Russian assent to the secret Sykes-Picot Agreement and its terms in regard to a future disposition of Palestine. There was little enthusiasm for the proposal on the part of either the French or the Russians. Brecher gives an account of French motivations and attitude to the question during the war years.
There were few developments until the change of government in Britain although the need for accommodation with the French, intent on sticking by the terms of Sykes-Picot, remained. In a memorandum dated 21 April 1917, Lord Robert Cecil, who was deputizing for Arthur Balfour as Foreign Secretary during the Balfour Mission to America, wrote that:
I quite recognise the very great difficult of carrying out the Zionist policy involving as it does a strong preference for a British protectorate over Palestine. That seems to me to make it the more desirable to get France to join us in an expression of sympathy for Jewish Nationalist aspirations.
A trip to France and Italy had been organized for Mark Sykes, who had been appointed earlier in the year to lead negotiations with the Zionists, and Zionist diplomat Nahum Sokolow, during April and May 1917. They secured the assent of Pope Benedict XV on 4 May 2017. Having met various French officials in April, they visited Italy and Sokolow secured the verbal support of Pope Benedict XV on 4 May 1917. On his return to France, Sokolow was able to obtain the French commitment in written form, the Cambon letter, although it remained unpublished at the time. The letter was apparently submitted to Ronald Graham by Sokolow; Picot was asked to come over to London by end of October to appear at a Cabinet meeting and explain the French position in relation to the Zionist movement. Kaufman cites Stein as considering it feasible the possibility that the document was not brought to the attention of Lord Balfour or that he forgot about its existence and also cites Verete as believing the document probably lost.
Kramer gives more information as well as an analysis of the background and motivations for the Cambon letter and the post-Balfour Declaration endorsement by Pichon.
- "French support for the Zionist cause in 1917". balfourproject.org. Balfour Project. Retrieved 14 June 2017.
- Vereté, Mayir (1970). "The Balfour Declaration and Its Makers". Middle Eastern Studies. Taylor & Francis, Ltd. 6 (1): 48–76. doi:10.1080/00263207008700138. JSTOR 4282307.
- Kramer, Martin (12 June 2017). "How the Balfour Declaration Became Part of International Law". Mosaic. Retrieved 14 June 2017.
- Brecher, F.W. (1993). "French Policy toward the Levant". Middle Eastern Studies. 29 (4): 641–663. doi:10.1080/00263209308700971.
- Friedman, Isaiah, The Question of Palestine: British-Jewish-Arab Relations, 1914-1918, Transaction Publishers, pp. 150–, ISBN 978-1-4128-3868-9
- Sanders, Ronald (January 1984), The high walls of Jerusalem: a history of the Balfour Declaration and the birth of the British mandate for Palestine, Holt, Rinehart and Winston, p. 507, ISBN 978-0-03-053971-8
- Sokolow wrote a description of the meeting, which is held in the Central Zionist Archives, but no record exists in the Vatican. Minerbi, Sergio I. (1990). The Vatican and Zionism: Conflict in the Holy Land, 1895-1925. Oxford University Press. ISBN 978-0-19-505892-5.. Friedman sources the quote to "CZA, A 18/26, Report, dated 4 May 1917, on an interview with the Pope". The note of the conversation includes the following exchange:
"His holiness: I am sure you did not come only as a matter of ceremony but as a representative of the Zionist idea. That has great significance. It refers to the rebuilding of Judea by the Jewish people — is that not so? What a historical turnabout. Nineteen hundred years ago Rome destroyed your country, and now, wanting to rebuilt it, you come to Rome.
Sokolow: I am deeply moved by these historical memories, which are so apt. Allow me the liberty to add that the Rome that destroyed Judea was duly punished. It vanished, whereas not only do the Jewish people live on, they still have sufficient vitality to reclaim their land.
His holiness: Yes, yes, it is providential; God has willed it."
Minerbi, Sergio I. (1990). The Vatican and Zionism: Conflict in the Holy Land, 1895-1925. Oxford University Press. p. 110. ISBN 978-0-19-505892-5.
The Vatican archives relating to this period do not contain any documents on these conversations, and as a result we are forced to rely solely on Sokolow’s account of his talks at the Vatican. These reports are necessarily subjective and more than once, contradict the policy adopted by the Holy See. It is not unlikely that on occasion Sokolow heard what he wanted to hear
- Kaufman, Edy (2006). "The French pro-Zionist declarations of 1917–1918". Middle Eastern Studies. 15 (3): 374–407. doi:10.1080/00263207908700418.