The Islamic State has not been defeated in Syria. But even if it had been, the durable defeat of that terrorist organization requires a continuing American military presence in Syria. Let's be clear, President Trump's pledge on Wednesday to withdraw all U.S. forces from Syria is a great gift to Syrian President Bashar Assad, Iran, Russia, and ISIS 2.0.

First off, let's consider what the U.S. military presence in Syria is and is not actually about. Because it's not about facilitating Assad's overthrow in Damascus. That effort ended years ago. Instead, the U.S. presence is about four other things: constraining ISIS cells (which are still operational, albeit in a covert fashion) and obstructing Russia, Iran, and (to a lesser degree) Turkey from their malfeasant purposes in Syria. There is no doubt that leaders in each of those capitals will be celebrating.

Moscow, in particular, has been desperate to see U.S. forces out of Syria. Russian President Vladimir Putin is furious about the U.S. military's ability to prevent Russia and Assad from dominating eastern and northern Syria for their own interests. Trump's excellent Syrian special representative Jim Jeffrey should resign. His leverage pulled out from under his feet, Jeffrey is destined to become Russian foreign minister Sergey Lavrov's new toy. Russia will double down on its absurdly false political reconciliation track in Syria.

That said, this isn't just about strategy; it's about human lives. Now that the U.S. deployment is ending, you can bet that Russia's Idlib slaughter will begin in short order. That Syrian blood will be Trump's companion to the Syrian lung matter that stains former President Barack Obama's foreign policy legacy.

Trump's gift to Iran is more obvious. Syria matters to the Iranian theocratic hard-liners because it offers them a land route from Tehran to the Lebanese Hezbollah bases in southern Lebanon (maybe the United Nations can lead in America's place?). And affording Iran control over both sides of the Iraq-Syrian border, this withdrawal also boosts the hard-liners' pernicious political influence in Iraq. The tragedy here is that U.S. diplomacy in Iraq has recently strengthened the hands of moderates in Baghdad. Trump says the Iran nuclear deal is bad, but he's given Tehran a gem of a political deal here.

That leads us to the ISIS 2.0 issue. Without the deterring constraint of U.S. forces, Assad's forces and Iran's militias will rampage their way through the very Sunni heartlands that ISIS once dominated. And the lesson of ISIS's post-2011 metastasis in Iraq is that where moderate Sunnis are forced to choose between Sunni death squads and Shia death squads, the majority will choose the latter. ISIS leader Abu Bakr al-Baghdadi will be clapping for Trump today.

Then there's Turkey. While an erstwhile U.S. ally, Turkey shares few U.S. interests in Syria. But President Recep Tayyip Erdogan has much to thank Trump for. His forces will now have free reign to crush the Kurdish YPG militia in northern Syria and Kurdish civilian communities along with them. Don't take my word for it, just consider what the Turks are doing right now.

To be sure, Trump has long wanted U.S. forces out of Syria. But his reasons for premature withdrawal were always just as vacuous as Obama's in Iraq. In neither case was the U.S. regularly taking casualties. But in both cases the U.S. military footprint provided outsize security and political benefits. It's a sad but telling irony that Syrian special representative Jeffrey was the ambassador to Baghdad back in 2011. History will render poor verdict on this particularly shallow tweet and the strategic incontinence it represents.

