US President Donald Trump officially recognized Jerusalem as Israel's capital on Wednesday, rebuffing the warnings of American allies throughout the Middle East.
Trump announced that the U.S. will move its embassy from Tel Aviv to Jerusalem, a decision that breaks with decades of Washington policy.
Saudi Arabia has called the move a "flagrant provocation," while Turkish President Recep Erdogan described Jerusalem's current status as a "red line for Muslims."
Recognizing Jerusalem as the capital of Israel was a Trump pledge during his electoral campaign. In defense of the move, his administration said: "We view this as a recognition of reality."
Some see Trump's stance as a pandering to his domestic conservative base, but why is recognizing Jerusalem, and not Tel Aviv, as the Israeli capital viewed as potentially dangerous?
Jerusalem: A history of worship and conflict
Founded 3,000 years before the birth of Jesus Christ, Jerusalem was transformed into a city of worship for Muslims, Jews, and Christians during the biblical era.
Its Old City houses sacred religious venues for all three faiths, including the Western Wall (sacred to Jews), the Church of the Holy Sepulchre (a pilgrimage site for Christians), and the Dome of the Rock (a 7th-century Islamic shrine).
The Old City is now a world heritage site, but modern-day Jerusalem extends far beyond its borders, with a wider population estimated at about 1.2 million people.
Israelis and Palestinians both claim Jerusalem as their capital and its status remains a key point of argument in the conflict between the two.
According to historians, the original kingdom of Israel emerged during the Iron Age. After a series of battles with neighboring empires, an independent Jewish Kingdom, Judea, was established before then being co-opted by the Romans.
Arab control of the area followed over several centuries, leaving the Jewish people without an officially recognized land.
A determination to reclaim a Jewish homeland was led by the Zionist movement and during World War I, the United Kingdom's foreign secretary, Arthur Balfour, announced support for the establishment of a "national home for the Jewish people" in Palestine.
After 30 years of this "British Mandate," a United Nations partition plan was devised for the area. In 1947, this resolution was adopted by the UN but never implemented as war broke out between Arabs and Jews.
This conflict led to the division of Jerusalem. Israel captured the west of the city while Arab-Jordanian forces annexed the city's east.
In the six-day war of 1967, Israeli forces then captured and claimed the east of the city. To this day, many countries do not recognize the whole of Jerusalem as an Israeli state and don't hold embassies in Jerusalem, choosing Tel Aviv instead.
It is therefore widely considered that Trump's relocation of the U.S. embassy to Jerusalem would recognize the city as Israel's alone, dismissing any Palestinian claim to seek East Jerusalem as a capital for a future state of its own.
That plan sits in alignment with the UN resolution to create a two-state solution for the region, offering an independent Palestinian state, along the boundaries set in place prior to the 1967 war.
The situation is further confused by Israeli settlements in the city's east that are considered illegal by international law, but not by the Israeli government.
It is estimated that about a third of families living in Jerusalem identify themselves as Palestinian.
Trump sparks reaction
Ahead of his announcement Wednesday, the U.S. president called several leaders in the region to forewarn them of the embassy move.
In addition to Saudi and Turkish dismay, the Palestinian leader Mahmoud Abbas warned that there would be "dangerous consequences" for the region and the world.
Egypt's President Abdul Fattah Al-Sisi also urged Trump not to "complicate the situation in the region".
Already, there have been protests in the streets with pictures emerging of Palestinians in Bethlehem burning pictures of Trump. A "day of rage" has also been called for this Friday by the Palestinian Sunni-Islamic fundamentalist organization, Hamas.
In expectation of violence, U.S. government employees have been barred from personal travel in the Old City and West Bank.