At the time, the Ottoman Empire still had most of the area of Palestine under its control, and the borders of what would become Palestine had been outlined as part of the 16 May 1916 Sykes-Picot Agreement between Britain and France. In exchange for the commitment in the declaration, the Jewish community would seek to encourage the United States to join World War I. That wasn't the sole reason, for there had long been considerable support in Britain for the idea of a jewish homeland, but the timing was influenced by the possibility.
The declaration read as follows:
An early draft used the word that in referring to Palestine as a jewish homeland, which was changed to in Palestine to avoid committing to it being the whole of Palestine. Similarly, an early draft did not include the commitment to not prejudicing the rights of the non-jewish communities. These changes came about partly as the result of the urgings of Edwin Montagu, an influential anti-Zionist Jew and Secretary of State for India, who, among others, was concerned that the declaration without those changes could result in increased anti-semitic persecution.
Like the preceding Sykes-Picot Agreement, the declaration is viewed by many Arabs as a gross betrayal of Britain's undertakings to support Arab independence in the Hussein-McMahon Correspondence of 1915-1916.
One of the main Jewish personalities who negotiated the granting of the declaration was Dr. Chaim Weizmann, the leading spokesman for organized Zionism in Great Britain. During meetings in 1906 between Chaim Weizmann and Balfour, the Unionist leader was impressed by Weizman's personality. Balfour asked Weizmann why Palestine - and Palestine alone - could be the basis for Zionism. "Anything else would be idolatry", Weizmann protested, adding: "Mr. Balfour, supposing I were to offer you Paris instead of London, would you take it?" "But Dr. Weizmann", Balfour retorted, "we have London", to which Weizmann rejoined "That is true, but we had Jerusalem when London was a marsh".
Weizmann was a chemist who managed to synthesize acetone via fermentation. Acetone is needed in the production of cordite, a propellant needed to lob artillery shells. Germany had a corner on a key acetone ingredient, calcium acetate. Without calcium acetate, Britain could not produce acetone and without acetone there would be no cordite. Without cordite, then Britain may have lost the Great War. When asked what payment Weizmann would like, Weizmann responded, "There is only one thing I want. A national home for my people". He received both payment for the chemical work and a role in the history of the origins of the state of Israel.