Indeed, Mr. Trump’s statement on Thursday was a major development. It is the final nail in the coffin of the 1967 line — the armistice line that separated Israel from its neighbors before the Six Days War. More than 50 years since this line was crossed by the Israeli military, we can finally kiss it goodbye.

The part of the Golan Heights controlled by Israel is a 500-square-mile territory wedged between northeast Israel and southwest Syria. Syria ruled this area until 1967. Then Israel occupied it. Since then, there have been about 50 years of negotiations, with Syria demanding the territory back and Israel demanding a peace agreement.

Many Israelis, though, knew that it never should — or would — be returned to Syria. The area was too important strategically and historically. In 1981, the Knesset passed a law essentially annexing the territory. And yet, negotiations continued, with successive prime ministers making overtures to the Syrians, until the Syrian civil war — and the takeover of much of Syria by Iran and its proxies — put an end to the charade.

Israel had no choice but to give up on the idea of withdrawing from the Golan Heights. But this reality involves a complete overhaul of the way the international community thinks not just about the Golan Heights but also about all the lands Israel occupied in 1967. The “land for peace” formulation for the past five decades has been a basis of all peace processes between Israel and Egypt, Syria and the Palestinians. Mr. Trump seems to have accepted the position of Israel’s government and given up on the idea that Israel has to withdraw to a decades-old line to get peace.

Withdrawal worked for Israel once, in 1979, when it signed a peace agreement with Egypt and left the Sinai Peninsula, which was also occupied in 1967. But that set a problematic precedent. President Anwar Sadat of Egypt insisted that Israel hand back the entire peninsula to the last inch. Israel decided that the reward was worth the price, as a major Arab country agreed to break with other Arab states and accept Israel’s legitimacy. But there was a hidden, unanticipated cost: Israel’s adversaries, in future negotiations, would demand the same kind of compensation. The 1967 line — what Israel controlled before the war — became the starting point for all Arab countries, including Syria. It became a sacred formula, worshiped by the international community.