Fool around, find out. After decades of terrorist attacks and eleven months of indiscriminate civilian bombardment, Hezbollah leadership belatedly discovered that it had touched off a real war with Israel. And then Hezbollah promptly lost its entire top leadership structure in less than two weeks:

Long-time Hezbollah leader Hassan Nasrallah and other top commanders of the terror group were killed in a massive Israeli airstrike on their underground headquarters in the Lebanese capital of Beirut, the Israel Defense Forces announced Saturday morning as Israel sought to dramatically upend the year-long conflict.

Hezbollah confirmed his death several hours later.

The announcement came as the Israeli military ramped up its airstrikes against Hezbollah assets in Beirut and other areas in Lebanon, hours after Nasrallah was struck at the terror group’s main headquarters, leaving parts of the Lebanese capital shrouded in smoke and dust.

In the wake of the announcement, Iran's Ali Khamenei called for Muslims to unite against Israel. But it's where the 'Supreme Leader' made that call that is most notable:

Iran's Supreme Leader Ayatollah Ali Khamenei called on Muslims on Saturday "to stand by the people of Lebanon and the proud Hezbollah with whatever means they have and assist them in confronting the ... wicked regime (of Israel)."

In a statement after the Israeli army said it had killed Hezbollah leader Hassan Nasrallah, Khamenei said: "The fate of this region will be determined by the forces of resistance, with Hezbollah at the forefront," state media reported.

He has been transferred to a secure location inside the country with heightened security measures in place, two regional officials briefed by Tehran told Reuters.

Looks like Iran has belatedly learned a lesson about Israeli capabilities, and their own relatively lack of the same. Despite decades of planning and resources, the Israelis easily penetrated Hezbollah communications and subterfuge, and not just in Operation Grim Beeper. They knew precisely where to find Nasrallah, and had no compunction at all in destroying Hezbollah's command center, even in a residential center of suburban Beirut. If the assassination of Ismail Haniyeh at an IRGC safe house in Tehran hadn't taught the Iranians a lesson about Israeli determination and will, yesterday's decapitation strike in Beirut certainly did.

Does Israel have that same capacity in Iran? Does Khamenei really want to find out?

The comment about Hezbollah being "at the forefront" of the "forces of resistance" might be a clue. Why not Iran itself? Israel has all but destroyed Hamas as a proxy army, although they still remain a potent terror group with their top leader still presumably alive. Hezbollah's entire upper echelons, not to mention its reputation, just got annihilated. Iran is the only effective force in the field now against Israel, but at least thus far, it doesn't appear that Khamenei is too anxious to take the field. 

That calculation comes in to better focus when one understands what the loss of Nasrallah means to Iran's mullahcracy. Nasrallah didn't just serve as the leader of Hezbollah; he was the capo di tutti capi of all Iran's proxies arrayed against Israel:

Nasrallah had grown to become the senior leader of Iran’s numerous proxies. He would often host Iranian officials, and he would also invite representatives from Hamas and Palestinian Islamic Jihad to Lebanon to coordinate their attacks against the Jewish state. He also sought to muster the Houthis in Yemen to threaten Israel, and he coordinated with Iraqi militias.

The Hezbollah leader had worked with other key Iranian-backed leaders in the region; in recent years, Iran has seen many of them killed. This includes Qasem Soleimani of the IRGC and Iraqi militia leader Abu Mahdi al-Muhandis. With those critical leaders off the table, Nasrallah was increasingly filling many shoes. Now those shoes are empty again.

Fool around, find out? Perhaps. If Khamenei expects to reconstitute Hezbollah as the forward force against Israel, consider the difficulty he faces in achieving that goal now. Israel didn't just pick off Nasrallah as they did with Haniyeh. The IDF destroyed their entire top command, disabled thousands of their lower-level commanders in Operation Grim Beeper, and have completely destroyed their organizational infrastructure in Beirut. They'll be hard pressed to stop the Lebanese Armed Forces from pushing them out of the country altogether at this point, thanks to a total disintegration of command-control capabilities.

But even if they stick around, who can lead them? Israel has wiped out all of Hezbollah's candidates for succession. Units are still conducting missile attacks essentially alone and without any coordination, making those left with initiatives into easy targets for the IDF. There's a very real risk now of a ground invasion that will scour the sub-Litani of Hezbollah's remaining assets, which means that even if Khamenei appoints a successor, there may not be much left to lead -- and not much credibility left to even try:

“Israel has declared war. It is a full-scale war, and Israel is using this opportunity to eliminate the leadership structure and destroy Hezbollah’s infrastructure,” said Fawaz Gerges, professor of international relations at the London School of Economics.

“They are breaking Hezbollah’s power. There’s no need to kill every member of Hezbollah, but if you destroy its combat structure and force them to surrender. It loses credibility,” Gerges said.

That is the key. Nasrallah didn't just get defeated -- he got humiliated. It took Israel less than two weeks to utterly vanquish Nasrallah once the Israelis treated this like a real war. They humiliated the mullahs of Tehran too, taking less than two weeks to completely destroy the upper levels of the organization that Iran built with so much money and resources over the last 45 years. Israel made them all look ridiculous in a region where tyrants cannot afford to be made to look ridiculous. 

Fool around, find out.