When President Barak Obama first made his controversial reference to the 1967 lines as the basis for future Israeli-Palestinian negotiations on May 19, 2011, he introduced one main caveat that stuck out: the idea that there would be “mutually agreed swaps” of land between the two sides. He added that both sides were entitled to “secure and recognized borders.” But the inclusion of land swaps also raised many questions.

Several months after Israel captured the West Bank and Gaza in the 1967 Six Day War, the U.N. Security Council defined the territorial terms of a future peace settlement in Resolution 242, which over the decades became the cornerstone for all Arab-Israeli diplomacy. At the time, the Soviets had tried to brand Israel as the aggressor in the war and force on it a full withdrawal, but Resolution 242 made clear that Israel was not expected to withdraw from all the territories that came into its possession, meaning that Israel was not required to withdraw from 100 percent of the West Bank.