So when President Trump announced that the Islamic State is almost 100 percent defeated and that it’s time to start bringing U.S. troops home from Syria, it was up to Mattis to explain that the current offensive is stalled and it will take months for the last bastion of ISIS resistance to be eliminated. Mattis has been noticeably taciturn during the public debate, in which the top commander overseeing Syria, Gen. Joseph Votel, carefully avoided contradicting Trump. Yet Votel has made the case that in Syria, “the hardest part is in front of us,” a reference to the stabilization phase that the president would just as soon skip and “let other people do it.”

SQUARING THE CIRCLE: Trump’s talk of a quick exit from Syria seemed directly at odds with Votel, who put the amount of Syrian territory liberated from ISIS at “well over 90 percent,” not the nearly 100 percent figure cited by the president, and with special envoy Brett McGurk who, at the same U.S. Institute of Peace event, stated categorically that the U.S. is going to complete the mission to defeat ISIS.

After a high-level meeting at the White House, press secretary Sarah Sanders issued a statement that tracked with McGurk’s formulation. “The military mission to eradicate ISIS in Syria is coming to a rapid end, with ISIS being almost completely destroyed,” Sanders said. “The United States and our partners remain committed to eliminating the small ISIS presence in Syria that our forces have not already eradicated.”

Sanders later said to reporters, “As the president’s maintained since the beginning, he’s not going to put an arbitrary timeline. He is measuring it in actually winning the battle, not just putting some random number out there. But making sure we actually win, which we’ve been doing.”

PREPARING TO LEAVE: Whether U.S. troops will leave soon depends on the definition of “soon.” Turkey is fighting some of the same Kurds the U.S. needs to finish off ISIS in the east, so it could be many months before the U.S. can declare victory. What Trump is signaling is that while he’s willing to stay and finish the job, he expects other countries to rebuild the areas devastated by the war on ISIS. “We will continue to consult with our allies and friends regarding future plans. We expect countries in the region and beyond, plus the United Nations, to work toward peace and ensure that ISIS never re-emerges,” the Sanders statement said.

AVERSION TO NATION-BUILDING: Leaving too soon means ISIS could become a threat again. But national security experts point out that Syria, which is riven by a seven-year civil war, is much different from Iraq in 2011, when the precipitous withdrawal of U.S. troops led to the rise of ISIS. Trump’s aversion to nation-building, something he campaigned on, is well-founded according to a number of military experts we talked to.

“If we stay any longer we will in effect be taking sides in a civil war. Up until now, we have avoided that because we focused on ISIS,” said Mark Cancian, a senior adviser with the Center for Strategic and International Studies. “It would be a classic example of mission creep, that is, we got into the war focused on ISIS, now we’re going to expand what we are doing to participate in a civil war and there’s a huge downside.”

U.S. SIDELINED: If a picture is worth 1,000 words, you need only look at the photo of Russian President Vladimir Putin, Iranian President Hassan Rouhani and Turkish President Recep Tayyip Erdogan warmly clasping hands at the conclusion of their summit on Syria to understand the U.S. does not have enough skin in the game to be a major player in Syria’s future.

“Why should any of these players defer to U.S. interests when the U.S. ability to shape events on the ground is limited by a tiny commitment,” said Stephen Biddle, who teaches military strategy at George Washington University. “The trouble is all the other actors have greater stakes than we do and greater investments than we do, and that means they have more influence over the outcome.”

GUARDING THE BORDER: Trump has signed a “proclamation” authorizing the deployment of the National Guard troops to support the Border Patrol in its mission “to protect our country and stop the stream of illegal immigration.”

The White House said the action is not unprecedented. “In 2012, President Barack Obama authorized the deployment of guardsmen to the border. President George W. Bush also authorized the deployment of 6,000 guardsmen to the border as a part of Operation Jump Start, assisting in operations which resulted in the arrest of more than 173,000 illegal aliens, the rescue of 100 persons, and the seizure of more than 300,000 pounds of drugs.”

It’s unclear how soon National Guard troops will show up along the southwest border to back up the Border Patrol. At yesterday’s briefing, Homeland Security Secretary Kirstjen Nielsen made it sound imminent, but in the next breath said none of the details has been worked out with state governors, who will be activating the troops under Title 32 authority.

Nielsen said the much ballyhooed “Trump effect,” which saw a precipitous 44 percent drop in unlawful border crossings in the first few months of his presidency, has faded as illegal immigrants have figured out how to game the system with requests for asylum. “We’ve recently seen the numbers of illegal border crossings rise from 40-year lows last April back to previous levels,” she said.

WHAT THE TROOPS WILL DO: The Pentagon already assists DHS with counternarcotics missions, infrastructure construction, persistent surveillance operations, training and aerial support. Nielsen said the next step is for border-state governors to review suggestions on how the National Guard can support the Border Patrol. The number of troops will be up to them. “It will be strong. It will be as many as is needed to fill the gaps,” Nielsen said.

What they won’t be doing is arresting anyone, or doing law enforcement on U.S. territory, which is prohibited under a 19th century law, the Posse Comitatus Act

BUT THEY COULD BUILD A WALL, SORT OF: The ostensible reason for the deployment of Guard troops is the president’s frustration at being stiffed by Congress over his demand for $25 billion to build a massive border wall that he promised Mexico would pay for.

Nielsen suggested that one of the military tasks assigned to the Guard troops might be some modest wall building. “What he meant was there are some lands that the Department of Defense owns right on the border that are actually areas where we see illicit activity. As part of what DoD does every day, in terms of force protection, we’re looking into options for the military to build walls on military installations on the border.”

Good Thursday morning and welcome to Jamie McIntyre’s Daily on Defense, compiled by Washington Examiner National Security Senior Writer Jamie McIntyre (@jamiejmcintyre), National Security Writer Travis J. Tritten (@travis_tritten) and Senior Editor David Brown (@dave_brown24). Email us here for tips, suggestions, calendar items and anything else. If a friend sent this to you and you’d like to sign up, click here. If signing up doesn’t work, shoot us an email and we’ll add you to our list. And be sure to follow us on Twitter @dailyondefense.