The U.S. government is America’s largest employer, with 2.4 million civilian workers as of January, excluding the postal service. The Trump administration has started cutting tens of thousands of jobs through a plan encouraged by Elon Musk’s Department of Government Efficiency that aims to reduce the size of government by $1 trillion this fiscal year, roughly 15% of last year’s spending. The goal is to cull a workforce that President Trump has said includes many people who aren’t doing their jobs. Oxford Economics, a data provider and consulting firm, estimates there will be 200,000 fewer federal workers by the end of 2025.

In the private sector, employment attorneys say, major companies can spend months analyzing workers’ job performance, position and skills before making big cuts. They enlist senior leaders to recommend which workers to keep, pore over union rules and smooth the process of applying for unemployment benefits for fired workers. Such forethought is key to ensuring the employees who remain can still get the work done, they say.

The Trump administration has adhered to few of those norms so far.

Managers say essential staff have been cut, and that the administration hasn’t followed detailed rules on how to enact widespread layoffs. Government agencies have granted voluntary buyouts to tens of thousands of people, fired probationary workers—a term for those who were hired or promoted in the past year or two—and are planning for deep reductions in the next few months. So far, many cuts haven’t taken into account workers’ performance or the necessity of their roles.

Two judges on Thursday blocked the firings of probationary workers at agencies including the departments of Agriculture, Energy and Veterans Affairs. Probationary workers have fewer protections against layoffs. Still, the firings need to go through the proper legal avenues, said U.S. District Judge William Alsup in California.

White House press secretary Karoline Leavitt said the Trump administration will immediately fight Alsup’s order. While some probationary employees are expected to return to their jobs as a result of the rulings, their ability to retain those jobs remains uncertain given the continuing legal fight and plans for deeper agency cuts.

Supporters of the overhaul say the government’s workforce was due for reinvention, with the last major effort taking place under President Clinton. Republicans have criticized agencies for allowing federal employees to work remotely well past the pandemic, a practice they say has made them less accountable. Trump has ordered workers to return to the office.

Trump in the Oval Office told reporters this month that he wanted to terminate “the people that aren’t working, that aren’t showing up and have a lot of problems.” He said the government was experiencing “bloat like nobody’s ever seen before.”

In interviews, more than 60 current and former federal workers said the wide slashing has worsened services Americans receive and hindered remaining staff working on areas like improving healthcare and lowering energy bills. It also has discouraged top talent from working for the federal government.

From schools to campsites

Staff cuts have reduced or slowed services for health, education and even operations like weather forecasting.

After facing years of bipartisan criticism from Congress, the Department of Health and Human Services late last year hired a transplant surgeon to help implement fixes to the system that regulates organ transplants.

Dr. Jayme Locke, who left her post at the University of Alabama Birmingham for the federal job, was recently fired as a probationary worker. Transplant experts had hoped she would preside over a new era of making improvements instead of just studying them. Dr. Locke declined to comment. HHS didn’t respond to a request for comment.

Weather balloons, which capture information on temperature, humidity and wind, aren’t going up regularly in Albany, N.Y., or Gray, Maine, and launches have stopped altogether in Kotzebue, Alaska, due to staffing shortages at the National Weather Service.

National Parks and other federal lands are cutting hours at visitor centers. More than 700 Park Service employees took the government’s resignation offer, according to an email to supervisors seen by The Wall Street Journal. Roughly 1,000 probationary employees were fired, according to the National Parks Conservation Association, a nonprofit advocacy group.

A spokeswoman for the Department of the Interior declined to comment on personnel numbers, adding that the agency is improving fiscal responsibility and efficiency. Yosemite will begin taking summer reservations for some campground sites next week. More may become available if operational capacity allows, according to a Friday post from an official park account. People familiar with the delay attributed it to staffing uncertainty. The spokeswoman said the park expects to share more details about reservations later this year.

Oregon’s Yaquina Head, a Bureau of Land Management shoreline area, cut hours, halted lighthouse tours and may see closures at the black-stoned Cobble Beach after losing three of seven members of its permanent staff, said Sabrina Gorney, one of the laid-off probationary workers.

“Visitors are going to find that their services are really limited,” said Gorney, 24, who had worked at Yaquina Head as a seasonal employee and in August was promoted to a permanent role making $21.50 per hour.

Gorney’s termination letter, viewed by the Journal, said her abilities didn’t meet the department’s needs. She received three performance awards in less than a year.

Victoria DeLano, 52, worked as an equal-opportunity specialist for the Education Department’s Office for Civil Rights. Based in Birmingham, Ala., she processed discrimination allegations against Southeast U.S. schools.

About a month after she was fired, OCR offices in San Francisco, Philadelphia, Boston, Chicago, Cleveland, Dallas and New York were eliminated as the Education Department cut about half of its workforce.

Complaints have piled up, slowing efforts to ensure school access for disabled children in an office where staff were already overworked, she said. “A child is not able to go to school right now until something is in place,” said DeLano, who has advocated against the cuts through her union, the American Federation of Government Employees.

OCR plans to use more mediation and a faster case-processing approach to address disability-related complaints and other harassment complaints, a spokesperson said.

“The dedicated staff of OCR will deliver on its statutory responsibilities,” said Madi Biedermann, the department’s deputy assistant secretary for communications.

Some offices have tried to hire back the fired workers. In March the Merit Systems Protection Board, an independent agency, paused the terminations of about 5,900 probationary workers in the U.S. Department of Agriculture. The agency said it would bring back those employees with back pay.

Jeffrey Grant, deputy director for operations at an entity within the Centers for Medicare and Medicaid Services, said 29 of his 82 fired employees were rehired—20 because of their specific responsibilities, the rest because they weren’t actually probationary. Some laid-off members of his team, he said, worked on improving the process of how Americans enrolled in insurance coverage under the Affordable Care Act.

He retired in anticipation of mass terminations and later wrote to HHS’s acting chief human capital officer that “every one of these people had the ability, knowledge and skills that we require to accomplish our work.”

Not ‘safe’

In many parts of the country, the Trump administration’s job cuts have hit services and constituencies that Trump pledged to protect.

Chief among them is the Department of Veterans Affairs, which plans to cut about 70,000 positions and has already laid off thousands. The agency employs about 470,000 people.

Fewer VA staff are handling veterans’ claims that will get them treatment for military-service injuries and mental health conditions, two current employees said. This has already resulted in veterans waiting longer to get treatment in North Texas, one said.

Fifteen homeless veterans getting services at a VA community resource center in Denver are now without their assigned housing advocate, Brett Taylor, who was laid off from his role finding apartments for clients and making sure they had deposits. Remaining staff, he said, are overworked already.

“You would think it would make sense to add more providers, add more people, to make sure the veterans were taken care of,” said Taylor, a 37-year-old Army veteran who served in Iraq.

One VA hospital in Detroit canceled programs meant to improve patients’ stability and range of motion after the firings of probationary workers, including Kara Oliver, a 33-year-old Navy veteran leading classes and monitoring participants’ health and progress.

Oliver, whose salary was about $48,650, realized she was laid off when she went into the office on Feb. 25 and couldn’t access her computer. She said she didn’t receive her termination letter—useful for filing for unemployment benefits—until March 5.

“I want to be there for my veterans,” she said. But the instability of federal work is making her unsure if she would take a federal job in the future. “It just doesn’t feel safe.”

VA press secretary Pete Kasperowicz said the agency has laid off 2,400 probationary employees in positions including publicists, interior designers and diversity, equity and inclusion officers. The positions amounted to half of one percent of the VA’s workforce, he added.

“The notion that these layoffs are causing issues across the department is false,” he said.

Performance reviews

Since Trump’s inauguration, the administration has gutted entire agencies, teams and categories of employees, only to add some back later. Early targets were the U.S. Agency for International Development and the Consumer Financial Protection Bureau. Officials have tried to wind down the divisions’ work and lay off many staff.

The CFPB, created in the aftermath of the 2008 financial crisis, investigates complaints from Americans who say their banks charged them improper fees or falsely advertised interest rates.

Matthew Pfaff, chief of staff of the CFPB’s Office of Consumer Response, said in a court hearing that more than 16,000 complaints—unprecedented in his memory—piled up when the division was ordered to stop work for weeks.

Layoffs also cut into the work. Among the fired CFPB workers was Milo Chang, 22, who joined the CFPB in June through a program that recruited college graduates to the public sector who may have otherwise sought lucrative jobs in consulting, technology or finance. His team last year analyzed complaints from Missouri to Texas from Americans pressured to refinance their mortgages at higher interest rates after a divorce or the death of a spouse. He learned Sunday he would be rehired due to one of the Thursday rulings but said his future employment remains unclear.

Other agencies have cut probationary employees for performance reasons, without reviewing their performance.

Traci DiMartini, a human capital officer for the Internal Revenue Service, said in a court declaration that it would have taken weeks or months to evaluate 6,700 probationary workers’ performance.

That didn’t happen: “This fact was discussed openly in meetings,” she said.

She refused to sign the termination notices and was put on administrative leave pending termination, in part because she was “insubordinate and uncooperative with the DOGE employees,” according to her declaration. The IRS didn’t respond to a request for comment.

Keith Camire, 48 years old, received one of those letters. He started in September at the IRS to streamline spending on IT. His co-workers, he said, are now scrambling to absorb the work.

Camire, in Milford, Penn., said he voted for Trump three times. He said he’s not opposed to downsizing the government but is against the indiscriminate manner in which the cuts are being made.

“Is it mission critical in the sense of police, fire, border security?” he said of the work he was doing. “No, but it’s essential to provide fiscal accountability and responsibility, which is what DOGE is about.”

Deeper cuts

Deeper cuts are expected in the coming months as agencies begin the next phase of the downsizing: a so-called reduction-in-force process that is a highly regulated exercise used infrequently in government. Agencies were told they had until last Thursday to outline how many positions would be cut through attrition, layoffs, a Trump-ordered hiring freeze and the proposed elimination of agencies’ functions.

One former senior government official described the process like baking a cake with 20-step directions and that leaders must read the rules countless times. Workers’ tenure, veterans status and performance must be taken into account during layoffs.

The Office of Personnel Management on Wednesday told agencies that collective-bargaining agreement provisions that “excessively interfere with management’s rights” to lay off employees aren’t enforceable. It urged agencies not to respond to every request for information from unions.

In a recent round of cuts, officials at the Energy Department could submit just 200 characters to justify positions, according to two people with knowledge of the process.

In February, teams identified probationary workers who were critical to public safety, the environment and health, or other mission-critical areas, a former official said.

Still, ultimately some fired probationary staff were essential to nuclear facilities, that person said. Though some were reinstated, the agency will now lean more on contractors.

The DOE is finding ways to maximize efficiency while upholding its mission of “unleashing American energy dominance and strengthening our energy security,” said Andrea Woods, an agency spokesperson.

Write to Lindsay Ellis at lindsay.ellis@wsj.com