Relations between Middle East heavyweights Iran and Saudi Arabia have been fraught for decades as they spar over regional influence and religion. Each considers itself to be the guardian of one of the two main branches of Islam: Saudi Arabia is a Sunni kingdom and Iran is Shiite. On Thursday the young Saudi crown prince dramatically threatened to acquire a nuclear weapon if Iran does so and likened its supreme leader to Hitler.
Here is a look over the high points of tension between the rivals.
Iranian revolution, war
After the Islamic Republic of Iran is established in April 1979 following a revolt, Sunni nations accuse Iran of seeking to “export” revolution to them.
Iraq attacks Iran in 1980, triggering an eight-year war in which Saudi Arabia financially backs the Iraq regime.
Pilgrims killed, ties cut
Security forces at the holy site of Mecca in Saudi Arabia crackdown in July 1987 on an unauthorized anti-US protest by Iranian pilgrims. More than 400 people, mostly Iranians, are killed.
Angry Iranians loot the Saudi embassy in Tehran and, in April 1988, Saudi Arabia breaks off diplomatic relations for several years. Its pilgrims are absent from Saudi pilgrimages until 1991.
Opposing sides in Syria, Yemen
As Arab Spring demonstrations sweep the region in 2011, Riyadh sends soldiers to Bahrain where Shiites are protesting. Riyadh accuses Tehran of stoking tensions.
The rival capitals square off again in 2012 as the Syria crisis erupts. Iran backs President Bashar al-Assad and provides him with military forces and funds to battle Sunni rebels.
Saudi Arabia backs the rebels but joins a US-led coalition fighting the Sunni extremist Islamic State group.
Saudi Arabia and Iran also take opposing sides in the Yemen conflict: in March 2015, Riyadh forms a Sunni Arab coalition to intervene in support of the Yemeni president, while Tehran backs the Shiite Huthi rebels.
Riyadh and Washington accuse Tehran of supplying weapons to the rebels, who from late 2017 fire several missiles towards Saudi territory. Iran denies the charge.
Deadly hajj stampede
A stampede at the Hajj annual pilgrimage in September 2015 leaves around 2,300 foreign pilgrims dead, including hundreds of Iranians.
Iran’s supreme leader Ayatollah Ali Khamenei says the Saudi ruling family does not deserve to manage Islam’s holiest sites.
Ties cut again
In January 2016 Saudi Arabia executes prominent Shiite cleric Nimr al-Nimr, a driving force behind anti-government protests, for “terrorism”.
Iran is furious. Protestors attack Saudi diplomatic missions in Iran, and Riyadh again breaks off relations.
Lebanon’s powerful Shiite militia Hezbollah, an Iran ally, is in March 2016 classified as “terrorist” by the Gulf Arab monarchies.
In November 2017 it is from Riyadh that Lebanese Prime Minister Saad Hariri announces his resignation, citing Iran’s “grip” on his country through Hezbollah. He later recants.
In June 2017 Saudi Arabia and its allies break off diplomatic relations with Qatar, accusing it of fostering too close ties with Iran and backing extremism. The claims are rejected.
Iran nuclear accord
In October 2017 Saudi Arabia says it backs US President Donald Trump after he refuses to certify the 2015 nuclear deal aimed at halting Tehran’s nuclear ambitions.
On March 15, 2018, Saudi Crown Prince Mohammed bin Salman warns in a US television interview that if Tehran gets a nuclear weapon, “we will follow suit as soon as possible”.
The prince also refers to Iran’s supreme leader as “the new Hitler”.
“He wants to create his own project in the Middle East, very much like Hitler who wanted to expand at the time,” the prince says.