As the US weighs joining Israel’s assault on Iran, questions are mounting over whether such an intervention could trigger regime change in Tehran – an outcome that risks splintering the country and sending shockwaves across the region.

Iran’s supreme leader, Ayatollah Ali Khamenei, who crushed internal threats repeatedly during more than three decades in power, now faces his greatest challenge yet. His archenemy, Israel, has secured free rein over Iran’s skies and is decimating the country’s military leadership and nuclear program with its punishing air campaign.