As a possible government shutdown loomed, President Donald Trump preemptively blamed Democrats for any negative fallout.

Trump charged that Democratic intransigence about how to renew Deferred Action for Childhood Arrivals, or DACA, was preventing an agreement on federal spending that would keep the government open — including the country’s defense forces.

"Because of the Democrats not being interested in life and safety, DACA has now taken a big step backwards," Trump tweeted on Jan. 12, 2018. "The Dems will threaten ‘shutdown,’ but what they are really doing is shutting down our military, at a time we need it most. Get smart, MAKE AMERICA GREAT AGAIN!"

....Because of the Democrats not being interested in life and safety, DACA has now taken a big step backwards. The Dems will threaten “shutdown,” but what they are really doing is shutting down our military, at a time we need it most. Get smart, MAKE AMERICA GREAT AGAIN! — Donald J. Trump (@realDonaldTrump) January 12, 2018

We won’t wade into the question of who would be to blame for the shutdown. However, we wondered whether Trump was correct that a government shutdown is tantamount to "shutting down our military."

When we checked with the White House, they said that Trump was not using the term literally, to suggest that the entire military will cease to operate. In other tweets, Trump used less sweeping language. In one, for instance, he warned against moves that would "stop paying our troops and government workers."

Still, the less cautiously worded tweet attracted nearly 23,000 retweets and almost 91,000 likes, so we thought it was worth a closer look.

What is a shutdown?

Federal government shutdowns occur when spending bills expire, and Congress and the president find themselves at an impasse. A law known as the Antideficiency Act requires suspending a federal agency’s operations until an appropriation bill is enacted. But there is some leeway to continue certain federal activities deemed essential.

A two-week shutdown occurred most recently in 2013, when Barack Obama was president, Democrats controlled the Senate, and Republicans controlled the House.

Prior to that, there were two shutdowns in the mid 1990s, when President Bill Clinton squared off against a new Republican majority in the House and Senate. One was for five days in November 1995, and the other was for 21 days, from December 1995 to January 1996.

Who works and who doesn’t

During the 2013 shutdown, as many as 850,000 workers were furloughed per day, or about 40 percent of the federal workforce (not counting active-duty military personnel and U.S. Postal Service workers).

The longstanding guidance is that "employees who are performing emergency work involving the safety of human life or the protection of property" remain on their jobs during a shutdown. The determination of who works and who doesn’t has traditionally been made by senior executives and legal advisors at each agency.

This means that the president, as the head of the executive branch, could theoretically order which federal workers must continue to show up for work, said Stan Collender, a budget specialist at the consulting firm Qorvis MSLGROUP.

During a shutdown, national parks typically shut their doors, government-funded scientific research is halted, and various health and safety inspections — by agencies like the Environmental Protection Agency and the Food and Drug Administration — are put on hold. (Some government functions are not reliant on congressional appropriations, and these can usually continue unimpeded in the face of a shutdown.)

But workers responsible for human safety and security will typically remain on the job, and that includes many members of the military.

How the military is affected

Active-duty military personnel have always been required to work through shutdowns. Army troops don’t abandon their posts and naval ships don’t all return to port. In addition, many civilian workers in the Defense Department have been required to work through shutdowns.

Other civilian workers in the Defense Department, however, hold jobs that do not meet the urgency threshold to keep working. In 2013, the government furloughed about half of its civilian workers, or about 400,000 employees, leaving a patchwork of various permissible and impermissible activities, according to Federal News Radio.

"We can and will continue to support key military operations," former Defense Department comptroller Bob Hale told Federal News Radio in 2013. "We’re allowed to do that by law, but the law would force us to disrupt many of our support activities. We wouldn’t be able to do most training, we couldn’t enter into most new contracts, routine maintenance would have to stop, and we couldn’t continue efforts to improve contracting and financial management including our audit improvement efforts."

The Defense Department, like other parts of the government, will experience some consequences from a shutdown. But experts we interviewed agreed that Trump’s language in this tweet amounted to an exaggeration, especially because the Defense Department is hurt less by a shutdown than most agencies.

"All critical military functions will continue," said Steve Ellis, vice president of Taxpayers for Common Sense. "There would be some wrinkles, but nothing like other areas of government."

Todd Harrison, a defense budget specialist with the Center for Strategic and International Studies, said the "biggest impact is probably on defense contractors, who will have to stop working." But "troops that are in harm’s way overseas will continue operating as normal and won’t be at any increased risk," he said.

Paychecks could be delayed

One way that even active-duty troops could feel the shutdown is in their wallets.

Employees who are required to work are not paid until a new spending bill is passed— effectively working for free, at least temporarily. Workers who are furloughed have historically been compensated for back pay through subsequent congressional action, though there is no requirement that such a bill be passed. In 2013, the Office of Management and Budget estimated that $2.5 billion in pay and benefits was paid for hours not worked government-wide, said Tyler Evilsizer, research manager for the Committee for a Responsible Federal Budget.

Usually, paychecks have been sent after a shutdown is over, but for the Defense Department in 2013, Congress and the president agreed to a bill in the middle of the shutdown that paid all active-duty and many civilian Defense Department employees. This enabled Defense Department employees to return to work while the shutdown was still going on for workers in other departments.

Delayed paychecks are just one downside of government shutdowns.

"A shutdown is a huge waste of taxpayer dollars, disruptive of government operations, and simply bad management," said John Palguta, a former federal human-resources official who is now an adjunct professor at the Georgetown University Public Policy Institute. "A shutdown, however, will not put the U.S. in harm’s way by shutting down our military."

Even just planning contingencies for a possible shutdown divert time and effort from the government’s duties, said Mallory Barg Bulman, vice president of research and evaluation at the Partnership for Public Service.

Our ruling

Trump said that in a government shutdown, "what they are really doing is shutting down our military."

This is an exaggeration. Based on historical precedent, the Defense Department does stand to see a substantial fraction of its civilian workers furloughed, and employee morale would likely suffer if paychecks are held back. But experts agreed that core military functions would remain operational, including all active-duty military personnel and many essential civilian workers.

We rate the statement Mostly False.