Just after nine o’clock on a recent morning, a group of camouflage-clad men swivel back and forth in black leather chairs around an arrow-shaped table inside U.S. Army Corps of Engineers headquarters in downtown Washington. A video display flickers in front of them.

A map appears on screen showing the latest modeling of the coronavirus’ spread through the United States. An orange and white blob swallows the Boston-region whole. “Wow,” says Lieut. General Todd Semonite, the Army Corps’ commander, his eyes widening. “We’d better stay on top of that.”

In March, Semonite was two months away from retirement, getting ready to end his 40-year Army Corps career and retreat to his home woodworking shop. Now, he’s the architect of a nationwide plan to build thousands of emergency hospital beds in states with critical shortages, converting convention centers, sports arenas and shopping malls into makeshift hospitals. In New York City, it’s the Javits Center. In Chicago, it’s McCormick Place. In Nashville, it’s the Music City Center. One-by-one, the sprawling buildings that usually host auto shows and comic conventions are being transformed into vast health care wards.

The “heat maps” that Semonite and his team review each morning give him a good idea of where his troops’ services may be needed next. Unlike the earthquakes, hurricanes and floods that the Army Corps typically responds to, the novel coronavirus outbreak is not a disaster contained to one area. “We need to be everywhere at once,” Semonite says. “We have some unbelievable data right now from every single state. We can click on a state and we can understand what the bed requirements are, what the beds available are, and then have some degree of an understanding.”

So far, the Army Corps has 17 construction contracts to add more than 15,500 beds in several states, but Semonite expects to do much more. Since Mar. 19, the federal agency, which is run by the military and employs an overwhelmingly civilian workforce, has inspected 834 facilities in all 50 states to determine whether the buildings there can be renovated into what the corps calls an “alternate care facility.”

Not every governor is ready to embrace the dystopian reality of their flagship urban buildings being converted into cavernous rooms of endless rows of white beds. But time is not on the states’ side, Semonite warns. Constructing a hospital from scratch can take weeks. He has dispatched his engineers to sit-down face-to-face with state and city leaders around the country to talk to them through their options — and to warn them that being a day or two behind the curve could be too late. “We’ve got to be smart enough to anticipate the need,” Semonite says. “We want to stay ahead of this and present these mayors and governors with their best options.”

Semonite leads an April 3 meeting at the Army Corps’s Washington, D.C., headquarters (Ray Whitehouse for TIME)
Semonite leads an April 3 meeting at the Army Corps’s Washington, D.C., headquarters
Ray Whitehouse for TIME

The first public call for the Army Corps’ help came on March 15, when New York Governor Andrew Cuomo called upon President Donald Trump to mobilize the organization to help build hospitals. Three days later, Semonite and his leadership team flew into New York City to meet with the governor. Faced with the city’s fast-growing caseload and shortage of beds, Semonite’s team knew they needed to act fast. On the 90-minute flight home to Washington, Semonite’s team decided rather than set up temporary field hospitals, as they’d done in the past, they would convert buildings that were already outfitted with electricity, elevators, fire protection, water and waste lines. “I couldn’t just pull a plan off the shelf to deal with this situation,” Semonite says.

Semonite, who previously led projects across Europe, Africa and the Middle East, asked Cuomo for a list of facilities that met the criteria. Javits Center was at the top of the list. With 1.8 million square feet of exhibit space, detachable wall partitions and hook-ups for plumbing and electricity every 10 feet, Semonite says the facility was ideal for what the Army Corps wanted to do. Design, engineering and construction for the more than 2,000-bed facility will be completed this week. The original plan for the building was to take non-COVID patients to free up space in maxed-out hospitals. But as the state’s number of COVID-positive patients flew past 90,000, Cuomo asked if Javits could be used to treat COVID patients.

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Semonite’s engineers made a few adjustments to the design, tweaking a ventilation system that now allows both COVID and non-COVID patients to be treated in the building with minimal risk of the disease spreading. The primary concern was airflow. Because COVID is a respiratory illness that transmits through droplets or aerosol generated from a cough, engineers need to be certain the air inside a COVID area wouldn’t mix with air outside. To do that, a “negative-pressure room” must be created to ensure particles drop to the ground rather than linger in the air. Engineers tinkered with the ventilation system to help with creating that vacuum whenever doors were opened or shut.

“The hardest part isn’t the engineering piece — that’s pretty easy,” Semonite says. “The hard part is decision-makers making decisions. If you’re a mayor and haven’t made a decision, you’re putting your people at-risk.” His blunt, straight-forward way of speaking could be seen as a liability in Washington, but the President has publicly praised Semonite, at the White House and on Twitter.

Army Corps officials believe that any future proposals for convention centers and sports stadiums will likely integrate pandemic-planning in its design. The facilities offer scale and efficiency for healthcare providers: doctors and nurses can supervise many patients at once, freeing up other workers to concentrate on the most severe cases at permanent hospitals. Trucks and buses can easily move people and supplies in and out, and the buildings are equipped with massive amounts of electrical power that are necessary to keep a hospital going.

Patients could begin arriving this week in Chicago where McCormick Place, North America’s largest convention center, which was converted into a 3,000-bed facility for COVID patients. Morial Convention Center, which served as a shelter for Hurricane Katrina survivors in New Orleans, is being converted into a 1,000-bed for COVID patients. The TCF Center, which was supposed to be hosting the Detroit auto show, will instead house a 1,000-bed field hospital with two separate floors for COVID patients. Nick Zager, chief engineer for the Detroit region, says TCF’s lower floor will have 400 beds for patients who are recovering and an upper floor with 600 beds for the seriously ill. “I’m from Detroit, born and raised here,” he says. “So it has given me a lot of hope to see everyone come together like this. I’m sure there’s a story like mine in every city.”

U.S. Army Corps of Engineers convert Detroit's TCF Center into an overflow hospital. (Penelope Carroll, U.S. Army Corps of Engineers)
U.S. Army Corps of Engineers convert Detroit's TCF Center into an overflow hospital.
Penelope Carroll, U.S. Army Corps of Engineers

All over the globe, officials have been forced to canvass for extra spaces to ease the strain on existing hospital systems. In Wuhan, the Chinese city where COVID-19 first emerged in December, officials converted one of its large sports complexes into a hospital as the outbreak worsened, and other nations have done the same. “It will be good for the U.S. government and others around the world to adapt what’s relevant from China’s experience,” says Dr. Tom Frieden, former director of the U.S. Centers for Disease Control and Prevention (CDC) and president and CEO of Resolve to Save Lives. “Tragically, this may be necessary unless the United States shelters-in-place soon and effectively.”

Health officials have seen more favorable U.S. projections for the COVID outbreak in recent days as social distancing practices and other mitigation efforts have slowed the infection rate. CenturyLink Field, the home field for the NFL’s Seattle Seahawks, hosted a 250-bed hospital for non-COVID patients, before Washington Governor Jay Inslee ordered it to close on Wednesday. Hours earlier, Governor Andrew Cuomo of New York said hospitalization figures were showing the state was “flattening the curve” of infection.

Despite these glimmers of hope, Semonite says he can’t relent on construction. There are too many variables regarding COVID’s spread. What is certain, however, is that any talk of his own retirement has evaporated. Instead of attending send-offs and cocktail hours with colleagues, Semonite is working 20-hour days and appearing on nightly news programs. And he is fine with that. “The President and Secretary of Defense will tell me where they want me to go and what they want me to do,” he says. “And when they call, and my phone rings, I will salute and do whatever they tell me. My job is to keep driving on.”

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Write to W.J. Hennigan at william.hennigan@time.com.