The United States’ withdrawal from the arms control agreement has heightened tensions and left the remaining signatories scrambling to keep the deal alive.

Conceived as the principal defenders of the 1979 revolution, the Islamic Revolutionary Guard Corps has evolved into an institution with vast political, economic, and military power.

The Taliban returned to power in Afghanistan in 2021, twenty years after their ouster by U.S. troops. Under their harsh rule, they have cracked down on women’s rights and neglected basic services.

Military experience gained from fighting in Syria’s civil war and decades of clashes with Israel have made the Iran-backed group stronger than ever, but the biggest threat it faces may be upheaval in…