In December 1917 — 100 years ago this month — the British general Edmund Allenby seized control of Jerusalem from its Ottoman Turkish defenders. Dismounting his horse, he entered the Old City on foot, through Jaffa Gate, out of respect for its holy status.

In the century since, Jerusalem has been fought over in varying ways, not only by Jews, Christians and Muslims but also by external powers and, of course, modern-day Israelis and Palestinians.

It is perhaps fitting that President Trump appears to have chosen this week to announce that the United States will recognize Jerusalem as Israel’s capital, despite concerns from leaders of Arab countries, Turkey and even close allies like France.

Conflicts over Jerusalem go back thousands of years — including biblical times, the Roman Empire and the Crusades — but the current one is a distinctly 20th-century story, with roots in colonialism, nationalism and anti-Semitism. The New York Times asked several experts to walk readers through pivotal moments of the past century. ...