This weekend, the United States and Israel carried out a massive air campaign against Iran, taking out hundreds of targets and killing Iran’s supreme leader, Ayatollah Ali Khamenei. This is a historic moment. A dictator who has terrorized the United States, the region, and his own citizens for almost 40 years has been eliminated. This weekend’s action is a measure of justice for his many victims.

But what comes next? To answer that question, it is important to first understand how we got here.

This weekend, the United States and Israel carried out a massive air campaign against Iran, taking out hundreds of targets and killing Iran’s supreme leader, Ayatollah Ali Khamenei. This is a historic moment. A dictator who has terrorized the United States, the region, and his own citizens for almost 40 years has been eliminated. This weekend’s action is a measure of justice for his many victims.

But what comes next? To answer that question, it is important to first understand how we got here.

Iran, of course, has posed one of the greatest threats to U.S. and global security for many decades. It is the world’s leading state sponsor of terror. It possesses the largest ballistic missile program in the Middle East and has a long-standing nuclear program. It is also a card-carrying member of the “axis of aggressors,” working closely with China, Russia, and North Korea, including by supplying Moscow with drones to brutalize Ukraine.

Nevertheless, the Trump administration was ready to move on from Iran and the broader Middle East after Operation Midnight Hammer, which badly degraded Iran’s nuclear program last summer. In its National Security Strategy and National Defense Strategy, released in December and January, respectively, the administration declared the Middle East largely resolved.

Then Iran made a number of grievous miscalculations. While Western commentators obsess over America’s mistakes, the past few weeks have been a case study in blowback, Persian-style.

When protesters rose up against the Islamic Republic in December, U.S. President Donald Trump drew a red line, warning the regime that it would “pay hell” if it “kills peaceful protesters, which is their custom.” He also promised the Iranian people that “help [was] on the way.”

The Islamic Republic murdered thousands of its own citizens in cold blood anyway. In recent days, critics have argued that Trump never made an effective case for war. But in my view, this was it, and after Trump’s warnings I concluded military action was inevitable.

Unlike former U.S. President Barack Obama’s unenforced red line over Syrian chemical weapons use, Trump was not about to back down. The Pentagon was not yet ready, however, because key military assets were deployed in the Western Hemisphere. It took until this weekend for the U.S. military to reposition its firepower and be ready.

In the interim, Trump saw an opportunity for a deal. Knowing that the world’s most powerful military was preparing to attack Iran, he thought Iran’s supreme leader might be willing to capitulate. Trump would have celebrated negotiating a nuclear deal with tighter restrictions than Obama’s flawed 2015 Joint Comprehensive Plan of Action. But Iran’s supreme leader stubbornly clung to his self-declared “right to enrich.” The ayatollah bet that he could ride out any attack—or at least go down as a martyr. He received one of these wishes.

The only remaining question then concerned the target set. I expected (and recommended in media appearances) that Trump would start with a limited strike on key Iranian military facilities as a first step to reinforce his red line. But Trump decided to go big. Having witnessed the vulnerability of the Iranian regime in January, Trump saw an opportunity to remove the Islamic Republic once and for all. The “prioritizers” and “restrainers” who populate the middle and lower levels of Trump’s national security bureaucracies and who see themselves as the true disciples of Trump’s foreign-policy vision must be pulling their hair out.

To be sure, this was a risky call. In past conflicts with the United States, like Operation Midnight Hammer last summer, Iran engaged in only token retaliation because it wanted to avoid a massive war with the United States. But now, with its back against the wall, there would have been little reason for Tehran to hold back. It could have conducted large-scale ballistic missile attacks throughout the region (possibly with chemical or biological warheads), closed the Strait of Hormuz, through which much of the world’s oil passes, or sponsored terror attacks throughout the world.

Some of those outcomes might still be possible, but so far Iran’s initial retaliation has been less coordinated and deadly than many feared. The United States and its regional partners have shot down or absorbed hundreds of Iranian missiles and drones with minimal casualties. Moreover, Iranian missile strikes on civilian targets in neighboring Arab nations have unified the region, and increasingly allies from around the world, against the Islamic Republic.

We also were reminded, once again, that China and Russia are ineffectual patrons. They could not save former Venezuelan President Nicolás Maduro, and they could not save Khamenei. Future dictators should be cautious about entrusting their security to Chinese President Xi Jinping and Russian President Vladimir Putin.

In his speech this weekend, Trump laid out a long list of military objectives, from eliminating Iran’s nuclear and missile programs to regime change. All of these goals are closer to being realized. Iran’s military capabilities are badly degraded, and the regime is on life support.

The world is safer than it was yesterday. Still, the major game-changer would be the collapse of the Islamic Republic. A better government in Tehran that respects the human rights of its own citizens and that cooperates internationally would be transformational for regional and global security.

Iran has been the primary source of instability in the region for the past several decades. With the Islamic Republic removed, the Middle East could become more peaceful, prosperous, and (dare I say it?) free. With the threat of simultaneous conflicts reduced, Washington could prioritize its rivalries with its more significant Eurasian rivals, especially China.

But there is a big gap between military strikes and a new, better government in Iran. The regime has demonstrated its willingness to kill to stay in power, and the Iranian people have not been willing to die in large enough numbers to seize it. Even with Khamenei gone, the remnants of the Islamic Republic may still be able to maintain control through murder.

But the security services could also change their minds. They might simply stand aside, as in the 2000 Serbian Bulldozer Revolution, and let the people rise up and seize the institutions of power. Trump tried to incentivize this outcome in his speech when he promised “total immunity” for security forces that lay down their arms.

Some fear that this weekend’s bombing will be the opening stage of a military quagmire for the United States like Iraq or Afghanistan. But this is unlikely. Trump’s “peace through strength” doctrine prizes short, sharp, decisive uses of force, and he is skeptical of long, drawn-out military campaigns. If this drags on too long, Trump will lose patience. His options at that point include declaring victory and going home, or attempting to negotiate with whatever strongman comes next, like he has done in Venezuela.

If the Iranian people are going to win their freedom, now is the chance. As Trump put it on Saturday, “Now is the time to seize control of your destiny, and to unleash the prosperous and glorious future that is close within your reach. This is the moment for action. Do not let it pass.”