Mr. Assad’s broadside was also a reminder that the perennial fractiousness of Arab politics goes deeper than disagreements on politics and religion. Syria’s differences with Saudi Arabia, which stem from Syria’s ties with Iran and its suspected role in an assassination in Lebanon in 2005, have been exacerbated by a personal feud between the Saudi king and Mr. Assad that began with Mr. Assad publicly insulting the king two years ago and is likely to be worsened by the bitter accusations of the past few weeks. Even where two countries share the same ideology and politics, personal differences between leaders have sometimes maintained a rift. Syria and Iraq were ruled for decades by the Baathist leaders Hafez al-Assad (Bashar’s father) and Saddam Hussein, whose rivalry kept their countries bitterly divided.

Image MEETING President Michel Suleiman of Lebanon, arriving in Doha. Credit... European Pressphoto Agency

“One of the problems with Arab politics is that it remains tribal and personal and that is why Arabs cannot agree about anything,” said Hilal Khashan, a professor of political science at the American University in Beirut.

Yet today’s inter-Arab tensions are not just about Gaza, or relations with the West, or even personal disputes. Many Arab leaders believe that Iran is aiming to become the dominant power in Middle East, and is using the Palestinian issue to batter its rivals through Hamas, its client.

“What’s happening in Gaza is dangerous on its own, but also dangerous in its implications,” said a Jordanian official who spoke on condition of anonymity because he was not authorized to discuss the issue. “Iran is interested in prolonging the violence, because that would help it to mobilize the Arab street and turn people here against their governments.”

That broad political threat to moderate Western-leaning governments may outweigh the sectarian anxieties provoked by Iran’s Shiite theology as its national power rises. Iran, after all, has now helped empower a Sunni Islamist movement, Hamas, as well as a Shiite Islamist movement, Hezbollah, and together the movements can claim a popular following across theArab world.

To many on both sides of the Arab divide, the battle in Gaza is a kind of replay of the 2006 war between Israel and Hezbollah. Then, as now, Israel mounted vastly more destructive attacks in response to the Islamists’ launching of rockets into populated Israeli areas. In a sense, the strategy worked: the Israel-Lebanon border has been quiet ever since. Even after the Gaza war began, Hezbollah restrained its militia from any attacks, knowing it could lose much of its political support within Lebanon if it were to draw the country into another devastating war. Now Israel, in Gaza, clearly hopes to limit Hamas’s future military options as well, mainly through agreements that could choke off its weapons supply network.

Yet the 2006 war strengthened Hezbollah politically, and the group now seems likely to win a majority in the parliamentary elections later this year, a pivotal development. Many people in Lebanon fear that the current war could bring similar new strength to Hamas, even as it inflicts political damage on its foes in the Arab world.