evidence: President Donald J. Trump’s recognition of Israeli sovereignty over the Golan Heights upends a half century of U.S. policy. The strategically important plateau has been widely considered under international law to be occupied territory since its 1967 seizure from Syria. In his proclamation, Trump cited security needs as paramount, though in practice Israeli control has not been challenged for decades. Experts warn the move could weaken international prohibitions on acquiring territory by force. [...] The seven-hundred-square-mile Golan Heights overlooks Israel to its west, Lebanon to its north, Syria to its east, and Jordan to its south. During the 1967 Six Day War, Syrian forces on the Golan Heights shelled Israeli farms in the Hula Valley below, and Israeli forces captured the territory from them following the Israeli seizure of the Sinai Peninsula and Gaza Strip from Egypt and the West Bank and East Jerusalem from Jordan. [...] Civil war in Syria since 2011 has given the Golan Heights new strategic significance for Israel. As President Bashar al-Assad’s grasp on power appeared tenuous, he bound himself to Iran and Hezbollah, the Lebanese Shia movement, to ensure his regime’s survival. Fighting between rebel and regime-aligned forces brought Iran’s Quds Force, an elite paramilitary unit, and Hezbollah militants to the edge of the Golan Heights. As Assad has consolidated his control, Israelis now worry that Iran and its proxies could maintain a permanent foothold there.