The British were awarded temporary administrative custody of a "Mandate of Palestine" by the League of Nations after the Ottoman Turkish Empire was defeated and dissolved by WW1. The 1920 treaty of San Remo divided that Mandatory territory along the Jordan river, awarding the eastern lands to Arabs (where Abdullah formed the Hashemite Kingdom of Jordan) and the western lands to Jews (where the state of Israel was declared).
It was the Jordanians that seized and occupied a portion of the Jewish land in 1948, though between 1920 and 1948 several international attempts were made to partition the Jewish portion further to limit the territory where the Jewish state could be established, trying unsuccessfully and foolishly to appease continuing Arab violence that just would not accept a sovereign Jewish presence.
The same foolish international efforts continue to this day, with all-too-similar results, when they should instead enforce the internationally-ratified San Remo treaty and devote humanitarian efforts to resettling Arabs outside of the Jewish territories and assisting the improvement of their well-being via education and economic aid both outside and inside Israel. To me, that sounds like a "peace-plan", though past history demonstrates that the enforcement actions likely will require unremitting suppression of Arab violence.