The Balfor Declaration

The Balfour Declaration of 1917 (dated 2 November 1917) was a formal statement of policy by the British government stating that

"His Majesty's government view with favour the establishment in Palestine of a national home for the Jewish people, and will use their best endeavours to facilitate the achievement of this object, it being clearly understood that nothing shall be done which may prejudice the civil and religious rights of existing non-Jewish communities in Palestine, or the rights and political status enjoyed by Jews in any other country."[1]

The declaration was made in a letter from Foreign Secretary Arthur James Balfour to Baron Rothschild (Walter Rothschild, 2nd Baron Rothschild), a leader of the British Jewish community, for transmission to the Zionist Federation of Great Britain and Ireland, a Zionist organization. The letter reflected the position of the British Cabinet, as agreed upon in a meeting on 31 October 1917. It further stated that the declaration is a sign of "sympathy with Jewish Zionist aspirations."

The statement was issued through the efforts of Chaim Weizmann and Nahum Sokolow, the principal Zionist leaders based in London; as they had asked for the reconstitution of Palestine as “the” Jewish national home, the declaration fell short of Zionist expectations.[2]
The "Balfour Declaration" was later incorporated into the Sèvres peace treaty with Turkey and the Mandate for Palestine. The original document is kept at the British Library.

The anniversary of the declaration, 2 November, is widely commemorated in Israel and among Jews in the Jewish diaspora as Balfour Day. This day is also observed as a day of mourning in Arab countries still today.

http://en.wikipedia.org/wiki/Balfour_Declaration_of_1917