Within hours of Israel launching strikes to assassinate Hassan Nasrallah, large posters appeared across Tehran declaring “Hizbollah is Alive”.

Iranian state media initially said Nasrallah, the Lebanese militant group’s leader, was “in a safe place”, but there was a conspicuous silence from regime officials. It was as if the Islamic republic’s leaders were not ready to acknowledge the loss of Tehran’s most important regional ally.

Israel’s assassination of Nasrallah on Friday delivered not just a catastrophic blow to Hizbollah, but a devastating hit to its main patron: Iran. For more than three decades, Tehran looked to Nasrallah and his movement as the key pillar in its regional security and deterrent strategy — the frontline in its long shadow war with Israel.