As the threat of a large-scale Russian invasion grows, Ukraine's government introduced a 30-day state of emergency, called up military reservists between the ages of 18 and 60, and voted to allow ordinary civilians to carry firearms.

• Ukrainian President Volodymyr Zelensky said yesterday that he doesn't expect an "all-out war against Ukraine" — but that he'll "put Ukraine on a war footing" if there is a "broad escalation" from Russia.

"Boy are they going to fight," a U.S.-based source in contact with the Ukrainian government tells Axios national security reporter Zachary Basu.

• "I do believe that the Russians don't quite understand what they're going to face."

Some Western officials have been puzzled that Zelensky hadn't taken such steps before now, or ordered a full national mobilization.

• The source said: "There's been this perception that they've been downplaying the threat, and that they're therefore not prepared. That's completely inaccurate."

What we're hearing: Zelensky and his team currently don't intend to relocate from the capital Kyiv to Lviv, in western Ukraine, to protect himself against what U.S. officials warn would be a devastating assault — complete with Russian missiles raining down on the city and the paralysis of electronic communications.

• "The president will not be running away from his own capital," a source close to Zelensky told Axios' Jonathan Swan.

But the mood in Kyiv is "much more nervous than it was even 48 hours ago," the source said.

• Go deeper: See our Ukraine-Russia crisis dashboard.

The federal government plans to test new vaccines that combine multiple strains of COVID to find what offers the best potential new booster, a senior Biden administration official tells Axios.

The catch: It's not clear whether another booster shot will be needed.

• Plus there are questions about who should receive one, and what kind of shot would be most effective, Axios' Caitlin Owens writes.

State of play: Fourth doses are already authorized for immunocompromised people. But for most people, a single booster shot appears to offer strong protection against severe disease, including from Omicron.

• Israel has already offered fourth shots. The U.K. soon will offer fourth shots to the elderly and some people with health conditions, The Sunday Times reported (subscription).

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Tech giants are betting billions that physical offices will be the future, Axios' Erica Pandey writes for our daily What's Next newsletter.

• Why it matters: Some of the world's most remote-capable companies are gobbling up office space and expecting employees to come back in person. That's a signal that fully remote work won't be the norm once the pandemic is behind us.

What's happening: Companies, real-estate analysts and workplace experts told The New York Times that factors propelling the trend include the hiring boom, the race to attract and retain top talent, "and a sense that offices will play a key role in the future of work."

• Meta, Facebook's parent, has leased huge new space in Manhattan, Silicon Valley, Austin, Boston, Chicago and Bellevue, Wash., The Times reports.
• Google last month announced the $1 billion purchase of a London office building.

Stunning stat: Tech companies held 36 of the 100 biggest U.S. office leases in 2021 — up from 18 in 2020, according to an analysis by CBRE, the global commercial real-estate services giant.

Coastal giants don't crack the top metro areas leading the post-pandemic jobs recovery, Axios' Erica Pandey writes from a report out today from Economic Innovation Group, which has Sean Parker among its founders.

• Superstar metros — New York, L.A., San Francisco and D.C. — are still magnets for talent. But a slew of smaller cities are joining their ranks.

Reality check: August Benzow, EIG's research lead, tells us that despite these metros' strength, all except Salt Lake City "still have significantly fewer leisure and hospitality jobs than they did before the pandemic."

• Phoenix has 25,000 fewer manufacturing jobs than it did in December 2019 — but gained 170,000 construction jobs.

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Demand for "green talent" is outstripping supply in all industries — not just in traditional environmental jobs, Axios' Joann Muller writes from new LinkedIn research.

• Why it matters: Green jobs now include a lot more than solar-panel installers and sustainability consultants.

More resumes are listing green skills like ecosystem management, environmental policy and pollution prevention.

• Some fast-growing green jobs include compliance manager, facilities manager or technical sales rep, LinkedIn's chief economist, Karin Kimbrough, writes.
• "It's everything from sustainable fashion — making fashion from sustainable materials — to architects thinking about: How do I create a building that uses more natural light so I don't have to cool it as much using air conditioning?" Kimbrough tells us.

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Two years ago today, Ahmaud Arbery was shot and killed while jogging down a suburban Brunswick, Ga., street. His death resonated nationwide after a video of the murder went viral months later, Axios Atlanta's Emma Hurt writes.

• In Arbery's native Glynn County, the effects of his death are translating into big change in the county's law enforcement and judicial system.
• Yesterday, three white men — who had already been sentenced to life for murdering Arbery — were found guilty of federal hate crimes.

County police officers responding to the scene didn't arrest the men present — even though two had guns, and literally blood on their hands.

• Two years later, the department has begun major structural changes, led by a new police chief. Jacques Battiste was sworn in as chief in December — the first Black person to hold the position full time.

The new chief tells Axios his goal is to help officers and the community "not only to heal but to begin to trust each other again."

• Keep reading.

The Gridiron Club, Washington's oldest association of journalists, will hold its 135th anniversary dinner April 2 — the group's first spring show in three years, USA Today's Susan Page tells me.

• Why it matters: With the white-tie Gridiron and the White House Correspondents' Association dinner on April 30 (with Trevor Noah as entertainer), Washington's in-person social circuit is back.

By Gridiron tradition, a luminary from each party delivers funny (hopefully) remarks.

• Gridiron President Tom DeFrank of National Journal will announce later today that the Republican speaker will be New Hampshire Gov. Chris Sununu.
• The Democratic speaker will be Rep. Jamie Raskin of Maryland, who spoke to the club's members-only Winter Dinner in December.

The Beijing Games had the smallest primetime audience of any Winter Olympics on record.

• An average of 10.7 million people watched in primetime over the past few weeks. With NBC's streaming and digital platforms, that ticks up to 11.4 million.

Why it matters: Viewership for major TV events, including awards shows and most sports championships, is falling fast, Axios Media Trends expert Sara Fischer writes.

• The massive exception: The Super Bowl remains hot as ever.

Go deeper: NBC's data.