In Damascus on the first Sunday of the new year, an unrepentant Bashar Assad stepped out of his bunker to announce that there was no end in sight to Syria's ordeal. "We are in a state of war in the full sense of the word," he proclaimed. The enemies of his Alawite regime, mostly Sunni jihadists and non-Syrians, he said, were the "enemies of the people and the enemies of God."
Next door in Iraq, on that same day, Izzat al-Douri, Saddam Hussein's loyal henchman and a man on the run since the 2003 U.S. invasion, turned up in a videotaped message on Al Arabiya TV. The former Baath Party leader announced his support for his Sunni kinsmen, some of whom had taken to the streets of Anbar province and Baghdad to protest the rule of Iraqi Prime Minister Nouri al-Maliki. Mr. Douri warned his Sunni brethren of a master plan, hatched by Mr. Maliki and his Shiite-controlled Dawa party, to "destroy Iraq and annex it to Iran."
On Syria's western border, in Lebanon, a country long in the orbit of Damascus, a Sunni community in hibernation has been stirred by the Syrian rebellion. Lebanon's second-largest city, Tripoli, has turned into a battleground between Sunni and Alawite militias. The Sunnis can now glimpse the possibility of their own restoration in Lebanon, a challenge to the writ and dominion of Hezbollah.
A struggle rages for a large swath of the Fertile Crescent, perhaps the most serious challenge to the borders of that slice of the Arab world since the European map makers stood up the states of Syria, Iraq and Lebanon in the aftermath of World War I.
Syria is the pivot of this tangled political space, which runs from the borders of Iran to the Mediterranean. Bashar Assad, the young, ruthless dictator in Damascus, had been certain that his country would be spared the turmoil of the Arab Spring—indeed he had dismissed that tumult as a "soap bubble" sure to burst.
Yet there is a greater irony behind the sectarian civil war that could bring down the Assad regime. During the Iraq War, the Alawite rulers in Damascus aided and abetted Sunni jihadists keen to do battle against the Americans and their Shiite supporters. With Syria ablaze, those jihadists, who see a chance to throw off the Alawite yoke, now war against Assad.
Meanwhile Iraq, the country that had been at the receiving end of Syrian-assisted jihadists for nearly a decade, supports Assad. The logic is sectarian through and through: Prime Minister Maliki and his Shiite coalition fear that a Sunni regime in Syria would spell trouble in Iraq's Sunni-dominated regions. Dispossessed of power by an American war and a Shiite coalition in Baghdad, Iraqi Sunnis were bound to see support for Assad as an affront to them, and as a tribute to the Iranian regime.
Iran's Shiite clerics don't rule Iraq, but the sense of Sunni disinheritance is a testament to the failure of the Maliki government to come up with a workable political compact among the principal communities. The bane of Iraqi history has been centralism, and the Maliki government has fallen into that malady. The domains of security and intelligence, and the armed forces, are all run out of the prime minister's office, where a willful and suspicious clique has virtually uncontested power.
Iraq's Sunnis are not alone in their discontent. Big Shiite players, Moqtada al-Sadr most notable among them, have signaled their determination to topple the Maliki government. To the northeast in Iraqi Kurdistan, military conflict hasn't broken out between Baghdad and the Kurdish Regional Government, but the protagonists have come close. The absence from the political scene of Iraqi President Jalal Talabani, due to a massive stroke, bodes ill for the peace between Arab and Kurd, for he was a master of the healer's art.
Western (Sunni) Iraq will not secede and cast its lot with the Sunnis of Syria, but if Baghdad's rulers want to maintain a semblance of peace, they will have to show greater appreciation of their country's temper and of its delicate demographic balance.
Lebanon lacks the power of the Iraqi state and the wealth of its central treasury. But in Lebanon, too, the Syrian rebellion has upended the political equation. The unfettered reign of Hezbollah cannot survive the fall of the Damascus dictatorship. The legend of the "axis of resistance" that Hezbollah used to ride herd over a Lebanese population is in tatters. In reality, it was the rule of the gun that had given Hezbollah its edge, but guns are plentiful, and the Sunnis of Beirut, Tripoli and Sidon are now capable of fielding their own militias. The racket that Hezbollah ran, with Syria's connivance, for nearly two decades is losing its power. The Shiites of Lebanon will of course endure, but they might begin to find a way out from under Hezbollah's warlords.
The Fertile Crescent's protagonists do not fight alone: On one side, there is the Iranian state, influential in Iraq and committed to the Syrian regime and to Hezbollah. On the other is the Sunni pact of Turkey, Saudi Arabia and Qatar. Egypt is of course a Sunni country but it has, due to its immersion in its own troubles at home, remained largely neutral in this struggle. This is a Sunni-Shiite fight, but religious devotion is not the measure of things. This is a very worldly grab for power and wealth and trade routes, and it is fought without sentimentalism or scruples.
This is a malady of that greater Middle East—its atavisms and ambitions. And to this malady, the United States today is a spectator.
Perhaps things would not be as they are if the Obama administration had opted for a residual U.S. presence in Iraq that would have checked the influence of Iran and given Baghdad greater assurance and nerve. Perhaps the conflict in Syria would have played out differently had we been spared the courtship of Assad in 2009 and 2010 by the Obama administration, and by an eager Sen. John Kerry, who ran interference for the administration.
With a more assertive American policy, perhaps a line would have been drawn for the Syrians in Lebanon. They had been banished from that country in 2005 thanks to the Cedar Revolution and to the "diplomacy of freedom" practiced by George W. Bush. The Syrians made their way back in 2009, the price for the Obama administration's "engaging" the dictatorships in Damascus and Tehran.
Say one thing about the people in the Fertile Crescent: If they had expected help and deliverance from the pre-eminent liberal power in the world, they now know better.
Mr. Ajami is a senior fellow at Stanford's Hoover Institution and the author most recently of "The Syrian Rebellion" (Hoover Press, 2012).