Analyzing America’s abandonment of its traditional role on the world stage, the former senator Joseph Lieberman assesses the resultant breakdown:

The simple fact is that there is more instability in the world today than at any time since the end of World War II. The threats come from emboldened expansionist powers such as Iran, Russia, and China, and also terrorist aggressors such as the Islamic State and al-Qaeda. In short, the enemies of freedom are on the march.

At the same time, the United States—which assumed global leadership after World War II to protect our domestic security, prosperity, and freedom—has chosen this moment to become more passive in the world. The absence of American leadership has certainly not caused all the instability, but it has encouraged and exacerbated it.

For example, . . .the military and political disengagement of the United States from Iraq after the success of the surge and our failure to intervene to stop the slaughter in Syria have conspired to create a vacuum in the heart of the Middle East. This vacuum has been exploited by the region’s most dangerous anti-American forces: totalitarian Sunni fanatics and the Islamic Republic of Iran.

The result is the creation of a terrorist sanctuary of unprecedented scale and Iranian domination over multiple Arab capitals. . . .

In too many places in recent years, the United States has treated its adversaries as essential partners to be courted, while dismissing or denigrating its historic allies and partners as inconveniences or obstacles to peace. But as frustrated as they are with the United States, our friends also recognize that they are incapable by themselves of managing the crises that confront them without the United States.

On the same day the cease-fire went into effect along the Israel-Lebanon border, rebel forces launched an unexpected offensive, and within a few days captured much of Aleppo. This lightening advance originated in the northwestern part of the country, which has been relatively quiet over the past four years, since Bashar al-Assad effectively gave up on restoring control over the remaining rebel enclaves in the area. The fighting comes at an inopportune moment for the powers that Damascus has called on for help in the past: Russia is bogged down in Ukraine and Hizballah has been shattered.

But the situation is extremely complex. David Wurmser points to the dangers that lie ahead:

The desolation wrought on Hizballah by Israel, and the humiliation inflicted on Iran, has not only left the Iranian axis exposed to Israeli power and further withering. It has altered the strategic tectonics of the Middle East. The story is not just Iran anymore. The region is showing the first signs of tremendous geopolitical change. And the plates are beginning to move.

The removal of the religious-totalitarian tyranny of the Iranian regime remains the greatest strategic imperative in the region for the United States and its allies, foremost among whom stands Israel. . . . However, as Iran’s regime descends into the graveyard of history, it is important not to neglect the emergence of other, new threats. navigating the new reality taking shape.

The retreat of the Syrian Assad regime from Aleppo in the face of Turkish-backed, partly Islamist rebels made from remnants of Islamic State is an early skirmish in this new strategic reality. Aleppo is falling to the Hayat Tahrir al-Sham, or HTS—a descendant of Nusra Front led by Abu Mohammed al-Julani, himself a graduate of al-Qaeda’s system and cobbled together of IS elements. Behind this force is the power of nearby Turkey.