President Trump has decided to cease U.S. support to moderate rebel groups in Syria. And it's a big mistake.

The president's decision will empower jihadism, Assad, Iran, and Russia. It will also fuel violent political sectarianism across the Middle East. And in all these things, it makes America less safe.

First off, losing their access to U.S. funding, weapons, and mentorship from the CIA, the rebels face absorption or destruction by jihadist groups.

Thanks to Trump, the Islamic State, al-Qaeda's Syria syndicate, and other Salafi-Jihadist organizations will remain the only well-funded groups fighting Assad's regime. That matters in that for many Syrian Sunnis, Assad is the enemy that must be defeated. And if necessary, otherwise moderate fighters will join jihadist groups in order to fight him. Trump has given these moderate rebels a binary choice: join the jihadists or accept Assad. They are highly unlikely to choose the latter. Trump talks tough on counter-terrorism, but this decision serves the exact opposite agenda.

As I've argued, the U.S. must support groups that counterbalance jihadist organizations for the mantle of Sunni resistance. If we do not, the jihadist threat will grow and any prospect for political moderation in Syria will evaporate. Do we seriously expect ISIS to cut a deal with the Syrian regime? Of course not. Trump has just shut down the only people who could have realistically come to the table for Syria's better future.

This decision is obviously also a win for Assad, effectively confirming his long-term survival in power. The focal issue here is that without a moderate Sunni opposition bloc, Assad will be able to unify the international community around his regime. This has been Assad's and Russia's intention the whole time: get rid of the moderates and then force the world to make a deal with the lesser of two evils.

And in that, it's also a big win for Putin. Trump has played perfectly into the former KGB colonel's hands. Just prior to meeting Putin at the recent G-20 summit in Germany, I warned that the Russian leader might offer a Syrian cease-fire in order to play Trump. He did just that. And now he's tricked Trump into doing far more: signing up to Assad's survival. It's a huge victory for Russia. One can understand why the Russians are optimistic that Trump will soon give back their spying mansions.

Then there's Iran. The hardliners in Tehran won big with Trump's decision. They can now point to their foreign policy aggression – supporting Assad's gas, barrel bomb, and starvation campaign as successful. And be under no illusions, this success will embolden the hardliners towards new aggression. This development, for example, will inspire the hardliners to keep playing games with the nuclear deal.

And that speaks to the final point.

How U.S. allies will react to Trump's choice.

Because now, in the absence of American influence to balance Sunni interests against Iran's Khomeinism, the Sunni monarchies will roll the sectarian dice. Obsessed by the perceived threat of Iran – as rendered in Assad's empowerment - they will throw money at Salafi-jihadists as a last resort counter-balance.

Just as Thucydides taught us that the cause of the Peloponnesian war was "the growth of Athenian power and the fear which this caused in Sparta," a major source of Sunni jihadism is the growth of Iranian power and the fear which this causes in Riyadh.

To be sure, the Sunni monarchies know that they cannot control the jihadists. But at the margin, they also know that the jihadists hate Iran and will attack its interests. As they see it, funding the jihadists is thus a deal with a demon in order to fight the devil. Yet with Trump pulling the rug out from moderate rebels, the Sunni monarchies are likely to move their support from the moderates and into the jihadists. They have long warned as much, and did so in the early years of the Syrian Civil War.

Correspondingly, Trump's wasteful short sightedness here cannot be overstated. The president has built a strong foundation (far stronger than his predecessor) with Saudi Arabia and the other monarchies. He has raised counter-terrorism and counter-extremism concerns to the forefront of Saudi foreign policy. He also has true partners in those nations who seek to advance their people from the grip of medieval political Islam to the opportunities of modernity.

With this one move, however, Trump is risking everything. Politicization of sectarianism is at the heart of the conflict in the Middle East. And Trump just gave it a booster shot.

Yes, critics of my argument will claim it seeks perpetual war neo-conservatism. But they are wrong. My argument is realist. It seeks the mitigation of threat by the tempered practice of American power. The moderate rebellion was a means to balance power politics in the Middle East and influence Russia towards political consensus in Syria. Now it is dead, and the extremists will dance in its ashes.

Unwitting subjects to Putin, Trump and his isolationist allies own the whirlwind that will follow.