Bloomberg | Bobby Ghosh: Any number of players — including Trump — could undermine the plan negotiated by Erdogan and Pence.

At first blush, it appears the five-day cease-fire in northeastern Syria puts Turkish President Recep Tayyip Erdogan in the catbird seat. If all goes according to the plan he worked out with U.S. Vice President Mike Pence, he will assume control of a significant swath of Syrian territory along the southern Turkish border.

Syrian Kurdish militias — which Erdogan regards as an existential threat to his country — are to withdraw to a “safe” distance of 20 miles, leaving space for millions of non-Kurdish Syrian refugees to resettle. In effect, this will create a human buffer between the militias and Turkey’s Kurdish territories, where the militias might otherwise stoke separatist tendencies. There should be an economic dividend, too: A lot of new building in the safe zone — homes, schools and other infrastructure for all those refugees — would be a boon for the Turkish construction sector.

What’s more, Turkey will face no penalties for invading Syrian territory and setting off a fresh wave of refugees; U.S. President Donald Trump will drop the mild economic sanctions his administration announced earlier in the week.

“We got what we wanted,” says Turkey’s foreign minister, Mevlut Cavusoglu.

Such optimism is, at best, premature. The deal was hastily put together without consulting many of the players in the long Syrian tragedy: the Kurds, the refugees, Syrian dictator Bashar al-Assad, Russian President Vladimir Putin, the Iranian regime and its proxies, the Arab states, the terrorists of Al-Qaeda and the Islamic State, and the U.S. Congress. Any of these protagonists can still undermine Erdogan’s ambitions.

Start with the people in his crosshairs. The Kurdish militias seem open to a temporary cease-fire, but they’ve made it clear they won’t tolerate a permanent Turkish presence in the safe zone. It’s hard to imagine them allowing Erdogan to demographically re-engineer their homelands without a fierce fight. In this, they will likely be supported by Assad’s forces and by fellow Kurds in Iraq. They will almost certainly receive covert assistance from Arab states, some of which will see it as fair turnabout for Erdogan’s support of the Muslim Brotherhood.

Nor is it a given that the Syrian refugees currently in Turkey will want to move into the Kurdish lands, where they might have to contend with two hostile forces: Assad’s army, which drove them from their original homes, and the Kurdish militias.

Assad has already moved his forces northward to block the Turkish invasion and take control of areas vacated by the Kurds. He will look to his patrons in Moscow and Tehran for backing; both Russia and Iran want Assad to regain full control of Syria, including the northeast.

Iranian President Hassan Rouhani has called on Erdogan to stop his military operation. More important, Iran has launched surprise military drills on its Turkish border (subtlety is not Tehran’s strong suit). And although Hezbollah, the terrorist group that has served as Iran’s catspaw in Syria, may be distracted by political upheaval in Lebanon, its fighters will be watchful for orders from Tehran.

For now, though, all eyes are on Putin. The U.S. military withdrawal from northeastern Syria represents a victory for the Russian leader, but he now faces a quandary. As much as Putin wants Assad to succeed, he is also keen to wean Erdogan away from the Western alliance. He must now decide which one to disappoint. Next week, Erdogan will meet Putin in Sochi, seeking the same concessions he was able to extract from Trump.

But the greatest threat to the Erdogan-Pence deal comes from the man who made it possible. In the space of two weeks, Trump has already performed two U-turns on Erdogan’s invasion — first enabling it, then sanctioning it, then effectively endorsing it. Now, as impeachment hearings draw near, Trump faces clamor in Congress for stronger action against Erdogan. Who would bet that Trump won’t change his mind again?

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.