If you ask President Trump, the United States is simultaneously bringing its troops home from Syria and securing “the Oil” (his capitalization) there.

In fact, the United States has neither brought home the troops — the military is in the process of pulling out most of them and re-stationing them in Iraq and elsewhere in the Middle East — nor completely left Syria. About 200, or 20 percent of the 1,000 troops in question, are set to remain in southern Syria.

So what’s going on? Let’s dive in.

What oil does Syria have?

Syria has very lucrative crude-oil fields centered primarily in the north and east near its border with Iraq.

Before 2011 — when peaceful anti-government demonstrations began, before descending into a bloody civil and proxy war — Syria was producing about 385,000 barrels of crude oil daily, according to David Butter, an associate fellow in the Middle East and North Africa Program at Chatham House. About 100,000 to 110,000 of those barrels came from fields in the northeastern Euphrates Valley, Butter said. This area includes the oil-rich province of Deir al-Zour, one of the early epicenters of protests against President Bashar al-Assad and where the Islamic State militant group later reigned.

Where is Syria’s oil coming from now?

Syria’s oil revenue was already falling before 2011 because of dropping global oil prices, but the market has taken a deep hit after nearly eight years of fighting that have destroyed Syria’s economy and infrastructure, alongside the hundreds of thousands of lives lost and people displaced.

According to Butter, Syria has been largely able to meet its daily demand for 150,000 barrels through imports from Iran, its oil-producing ally, and production in government-controlled areas.

You may recall that the European Union and the United States have imposed sanctions on oil deliveries to Assad’s government, which has been accused of committing war crimes against its citizens. You may also recall that there has been much high-stakes drama in the Mediterranean Sea over Iranian ships suspected of delivering oil to Syria, nonetheless. In recent months, Europeans have seized two Iranian tankers suspected of heading to Syria: After releasing one on guarantees that it wouldn’t sell to Syria, British authorities allege that it did, anyway. (Iran has denied the trade.)

The Syrian Democratic Forces (SDF) — the American-backed Kurdish-led force that U.S. troops had been stationed in northeastern Syria to support until two weeks ago — controls oil fields in the northeast and along the Euphrates River valley. These areas, in theory, could produce about 60,000 barrels a day, though Butter said it’s unclear whether there is any significant production at present.

What does the Islamic State have to do with it?

When the Islamic State swept across Iraq and Syria in 2014, it took control of strategic oil fields in both countries. The militant group subsequently turned a profit by selling oil at about $100 a barrel to black market traders or refining it in local makeshift facilities, according to Butter. In 2015, the Treasury Department estimated that the group made about $40 million a month, or nearly $500 million a year, from producing and exporting oil.

U.S. and European officials have even accused Assad’s government of buying oil from the Islamic State, according to the Wall Street Journal, as the two enemies fed off each other.

Where do U.S. troops come in?

U.S. airstrikes and material support to the SDF were critical in helping Kurdish forces oust the Islamic State and retake northeastern Syria in 2017. (Some of the land the militant group had seized was controlled by the Syrian Kurds and part of the semiautonomous government they set up in 2013.)

Until two weeks ago, some U.S. troops had been helping the Kurds maintain control of the territory, including the oil fields.

What’s the main threat to Syria’s oil fields now?

This part is more uncertain.

Defense Secretary Mark T. Esper told reporters on Monday that the remaining U.S. troops stationed around unspecified oil areas in Syria were intended “to deny access, specifically revenue to ISIS and any other groups that may want to seek that revenue to enable their own malign activities.”

The Islamic State, also known as ISIS, was severely weakened when it lost control of territory in Syria and Iraq — but it’s not entirely defeated, as Trump has repeatedly claimed he did. There is, nonetheless, still fear that supporters of the group might try to attack oil fields or jeopardize them, as they’ve already claimed they have done to farmland.

But Assad — who, while weakened, has survived as leader throughout Syria’s civil war — also no doubt wants a piece of the oily pie. In February 2018, Russian paramilitary mercenaries and pro-Assad forces attacked an SDF-controlled oil field near Deir al-Zour; a handful of U.S. Marines there helped to repel the attack, and the melee left 200 to 300 on the other side dead, according to documents obtained by the New York Times. This could be a harbinger of battles to come.

Meanwhile, Russia’s Ministry of Foreign Affairs declared Wednesday that the Syrian government should get back control of all of north-east Syria’s oil facilities, Reuters reported.

Still, more of Trump’s statements on the matter don’t entirely match the reality on the ground. The president has said that Israel and Jordan asked him to keep some troops in southern Syria, along the border with Jordan, which isn’t one of Syria’s oil-producing areas.

Many in the Middle East, moreover, are skeptical of U.S. presidents claiming they need to maintain troops on the ground in the region to protect oil on behalf of the local population — cue the Iraq War.

Trump didn’t help to assuage skepticism by also throwing out the idea Monday that U.S. companies could move in. (One of the many barriers to this: Oil production, like much in Syria, is state-owned and controlled by Assad’s circle.)

“We’ll work something out with the Kurds so that they have some money, so that they have some cash flow,” Trump said. “Maybe we’ll get one of our big oil companies to go in and do it properly.”

Kareem Fahim contributed to this report.