Now analysts and diplomats are scrambling to figure out what the latest developments mean, whether they are connected and whether, as some analysts fear, they are part of a buildup to a regional war.
Mr. Hariri, until he announced his resignation on Saturday, had shown no signs of planning to do so.
Hours later, on Saturday evening, a missile fired from Yemen came close to Riyadh before being shot down. Saudi Arabia later blamed Iran and Hezbollah for the missile, suggesting that they had aided the Iran-aligned Houthi rebels in Yemen to fire it.
Before the world had a chance to absorb this news, the ambitious and aggressive Saudi Arabian crown prince, Mohammed bin Salman, ordered the arrest of hundreds of Saudis — including 11 princes, government ministers and some of the kingdom’s most prominent businessmen — in what was either a crackdown on corruption, as Saudi officials put it, or a purge, as outside analysts have suggested.
It then emerged that the week before, Jared Kushner, President Trump’s son-in-law and adviser, who has been sent on missions both to Israel and Saudi Arabia, had visited Riyadh on a previously undisclosed trip and met until the early morning hours with the crown prince. The White House has not announced what they discussed but officials privately said that they were meeting about the administration’s efforts to forge an Israeli-Palestinian peace deal.
On Monday, Saudi officials said they considered the missile from Yemen an act of war by Iran and Lebanon, and on Thursday the kingdom rattled Lebanon by ordering its citizens to evacuate.
No one expects Saudi Arabia, which is mired in a war in Yemen, to start another war itself. But Israel, which fought a war with Hezbollah in 2006, has expressed increasing concern about Hezbollah’s growing arsenal on its northern border.
On Friday, Hezbollah’s leader, Hassan Nasrallah, said that Saudi Arabia had asked Israel to attack Lebanon, after essentially kidnapping Mr. Hariri.
Analysts say a new war in the region is unlikely but some have warned that the increased tensions could provoke an economic crisis or even start a war accidentally. Miscalculations have started wars before, as in the 2006 war between Israel and Hezbollah.
Experts caution that Israel is often only a mistake or two from being drawn into combat.
“It’s a dangerous situation now,” said Amos Harel, the military reporter for Haaretz, the Israeli newspaper. “It only takes one provocation, another reaction, and it can get all of a sudden completely out of control. And when you add the Saudis, who evidently want to attack Iran and are looking for action, it gets even more complicated.”
