The missile was fired from neighboring Yemen on Saturday by the Houthis, a rebel group with ties to Iran that has been battling a Saudi-led military coalition. The war has spawned countless cross-border attacks - including Houthi ballistic missile launches and thousands of Saudi airstrikes across Yemen - as well as an endless string of recriminations between the Saudi and Iranian governments.
But several factors seemed to make the latest Saudi warning more dire, raising fears of a military escalation between the regional superpowers. Though it caused no casualties, the missile strike was among the deepest yet into Saudi territory during Yemen's civil war, highlighting the Saudis' continued vulnerability to such attacks despite an overwhelming military advantage over the rebels.
And it came at a time when the crown prince, Mohammed bin Salman, and the rest of the Saudi leadership appeared to be escalating an offensive against regional adversaries such as Iran as well as domestic challengers. The Saudi authorities carried out an unexpected and withering purge Saturday that targeted princes, senior officials and the country's most prominent businessmen, shocking seasoned observers of the kingdom.
The arrests were cast by the authorities as part of an anti-corruption drive but struck many as the latest attempt by Mohammed to consolidate his power before eventually inheriting the throne from his father, King Salman.
In recent days, the Saudis have also stepped up their confrontation with Hezbollah, the Shiite party in Lebanon that is backed by Iran. The Saudis appear to have played a central role in the resignation of Lebanon's prime minister, Saad Hariri, who sharply criticized Iran during a resignation speech he delivered Saturday from the Saudi capital.
The Saudis have clearly been emboldened by support from the Trump administration. President Trump has repeatedly praised King Salman as the leader of the Arab world and a bulwark against what he has described as Iranian hegemony.
Currently traveling in Asia, Trump turned to Twitter on Monday to offer his strong support for the arrests and firings over the weekend, tweeting that "some of those they are harshly treating have been 'milking' their country for years!" and saying that "I have great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing."
Presidential adviser and Trump son-in-law Jared Kushner has cultivated a special relationship with Mohammed, and he has traveled to the kingdom three times this year, most recently on an unannounced visit 10 days ago. Kushner, along with negotiator Jason Greenblatt, is leading the administration's efforts to jump-start the moribund Israeli-Palestinian peace process. That goal will become more achievable, the administration believes, if the Saudis and Israel can be brought together based on their shared antipathy toward Iran.
In a series of messages posted Monday on Twitter, Iranian Foreign Minister Javad Zarif said that the Trump administration's support for Saudi Arabia has "proved hazardous to regional health." Following Trump's visit to Riyadh in May, Zarif noted, Saudi ally Bahrain launched a violent crackdown against a Shiite opposition stronghold, and Saudi Arabia, Bahrain and the United Arab Emirates broke relations and closed their borders with neighboring Qatar.
Trump has also praised Saudi Arabia for a pledge, made during his visit there, to spend $110 billion on future U.S. weapons purchases. In a news conference Sunday with Japanese Prime Minister Shinzo Abe, the president noted that Japan was "going to be purchasing massive amounts of military equipment" to defend itself against North Korea. It was U.S. antimissile defense systems, Trump said, that "shot something out of the sky the other day in Saudi Arabia . . . a needle in the sky, and it was hit immediately and exploded without damage."
In a call to Salman on Saturday, while Trump was en route from Hawaii to Tokyo, the president personally appealed to the Saudi ruler to list the upcoming sale of the Saudi Arabian Oil Co., Aramco, on the New York Stock Exchange. The Aramco sale, Trump told reporters aboard Air Force One, "will be just about the biggest ever," and the United States wants "to have all the big listings."
A White House readout of the call made no mention of the arrests in Saudi Arabia.
They swept up some of the country's most influential figures, including Prince Alwaleed bin Talal, a billionaire investor, as well as cabinet ministers and the head of the elite National Guard - a potential rival to the crown prince.
A royal decree named Mohammed the head of a new committee fighting graft, putting him at the center of an initiative popular with many Saudis - a move that also served to solidify the crown prince's hold on power.
In an analysis released Monday, the Eurasia Group said that "the dismissal and arrest of dozens of ministers, royal family members, officials and senior military officers represents the beginning of a national purge that will likely succeed in removing the last few obstacles standing between Mohammed bin Salman and the throne."
"The fact that the crown prince was able to arrest so many royals reinforces our view that his control over the security services is extensive and his rivals have failed to protect themselves," the report said.
Not everyone agreed. A former U.S. intelligence official said that the 32-year-old crown prince, who is often referred to by his initials, MBS, was out "over his ski tips" after arresting so many influential Saudis.
"His arrogation of power and authority, which is inconsistent with how the royal family and monarchy have functioned over many decades, will inevitably lead to trouble," the official said.
The escalating feud with Iran was emerging as the critical test for the crown prince, who has stumbled as the architect of Saudi Arabia's increasingly aggressive foreign policy initiatives, including the boycott of Qatar and the war in Yemen.
More than two years after the Saudis began a military campaign against the Houthi rebels and their allies, the war is at a stalemate. More than 10,000 Yemeni civilians have been killed, including a vast number as a result of Saudi airstrikes. The Saudis have yet to achieve any of their initial aims, including the restoration of the deposed Yemeni government, or the halting of ballistic missile strikes into Saudi territory.
On Sunday, the Saudis also offered bounties totaling more than $400 million for information on the whereabouts of 40 men who it said were "responsible for planning, implementing and supporting the Houthi terrorist group's various terrorist activities." The list included a $30 million bounty for information on the Houthi's leader, Abdulmalik al-Houthi.
The Saudis squarely blamed Iran for the missile strike, in a statement Monday carried by the Saudi Press Agency. "Experts in military technology," it said, had "confirmed the role of Iran's regime in manufacturing these missiles and smuggling them to the Houthi militias in Yemen."
It added that the government of Saudi Arabia "reserves its right to respond to Iran in the appropriate time and manner." Iranian officials denied any connection to the missile strike.
In their statement Monday, the Saudis announced that they were temporarily closing all Yemeni ground, air and sea ports - tightening a blockade that aid workers said has contributed to a devastating humanitarian crisis in Yemen.
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