In July 1987, the annual Hajj pilgrimage turned into one of the bloodiest flashpoints in the history of Islam's holiest cities.

A protest march by Iranian pilgrims in Mecca ended in clashes with Saudi security forces.

More than 400 people died.

The dead included hundreds of Iranians, and the tragedy scarred the pilgrimage far beyond that season.

For Tehran, the incident was the "proof" that the Saudi rulers were "not competent custodians" of Mecca and Medina.

The Ayatollah's Shia regime said that the House of Saud, under King Fahd bin Abdulaziz Al Saud, was a political actor who "controlled" the holy cities.The mistrust was not recent.

It was shaped by the Sunni Saudi monarchy and the Shia regime in Iran, which was established after the 1979 revolution.

The glimpses of the Iran-Saudi rivalry were recently seen in the ongoing war in the Middle East.

After Israel and the US hit Iran, Tehran targeted its neighbours, including Saudi Arabia.

An attack on Riyadh with a ballistic missile made Riyadh warn Tehran of a military response.

A Shia Iran and a Sunni Saudi Arabia have long fought for dominance in the Middle East.The hostilities sharpened after the Iranian Revolution of 1979.

The mistrust and bad-blood over Saudi's "control" of Mecca and the Medina never really faded.

Over the decades, Iran has accused Saudi Arabia of mismanaging the Hajj, especially after disasters such as the 2015 Mina stampede (which resulted in the death of more than 2,000 individuals).

Tehran has attacked Riyadh over what it calls the monopoly over the administration of Islam's holiest sites.

Saudi Arabia, for its part, has insisted that the management of Mecca and Medina and the pilgrimage is a matter of sovereign responsibility.That, in turn, raises the question, how did the House of Saud, who did not earlier rule the Hejaz region that had Mecca and Medina, come to become their custodians?Before the Saudis took over the Hejaz region in 1924-25, the holy cities had long been under Ottoman sovereignty.

The Hashemite sharifs ruled locally.

And for a brief period after World War I, Mecca-Medina and the region were part of an independent Hashemite Kingdom of Hejaz.Ibn Saud's eventual takeover was not just because of its military conquests.

The British backed him during his rise and the Wahhabi clerics provided him with religious legitimacy.The Kingdom of Saudi Arabia was, in fact, born in 1932.

It is true that Mecca and Medina are far older than Saudi Arabia, the modern state.

The two holy sites were not originally part of the House of Saud's territory.

They came under Abdulaziz Ibn Saud only after his military expansion from central Arabia into the Hejaz in 1924-25.

Later in 1932, all the territories in the Arabian Peninsula were folded into the Kingdom of Saudi Arabia as Saud unified them in his bloody campaigns.WAS MECCA AND MEDINA ALWAYS PART OF SAUDI ARABIA?The holy cities of Mecca and Medina long predate the modern Saudi state.

For centuries, they have been ruled by powers other than the House of Saud.

Located in the western mountainous coastal region of Hejaz along the Red Sea, the two cities....