One hundred years ago, the Balfour Declaration was issued by Arthur Balfour, the British foreign secretary. This document promised British support for “the establishment in Palestine of a national home for the Jewish people,” and was later reinforced with the support of most other western nations.
Obviously provocative at the time, this document and the events it sparked remain contentious to the present day because of the ongoing conflict over the territory now known as Israel.
The issue for Israelis is clearly one revolving around the physical land. Without the declaration, there may very well be no Israel at all.
On the other end of the spectrum, Palestinians are concerned about land, which they had previously occupied, and also argue that the resulting order has left them with diminished rights vis-à-vis their Israeli counterparts.
As an issue that ignites passion on both sides, disagreement over the Balfour Declaration is unlikely to subside.
To read a detailed account of the present-day fault lines over this issue, see more here: Balfour Declaration of Support for Jewish Homeland Still Divisive at 100