How a Gen Zer built a $3.7 billion defense tech startup backed by Sequoia

Hi, it’s Preston Fore, in for Allie. Earlier this month, defense tech firm Mach Industries raised $600 million in a Series C extension at a $3.7 billion valuation.

That’s more than double the $1.8 billion valuation Mach reached just three months earlier when it raised its initial $300 million Series C led by Ribbit Capital, Infinite Capital, Bedrock Capital, and Sequoia Capital. But perhaps more striking than the pace of the raises is who’s leading them: Mach, which builds autonomous defense systems, is run by a 22-year-old.

Founder and CEO Ethan Thornton launched Mach in 2023 at 19, after developing an interest in defense as a teenager. Since then, he’s built the company around a willingness to move quickly, take risks, and adapt as its technology and the broader defense industry evolve.

“You’re never going to know everything, especially when you’re starting young, and you shouldn’t expect to,” Thornton told Fortune. “If you wait until you have all the answers, you’ll probably never start.”

By 2024, Mach landed a deal with the Army Applications Laboratory to develop a vertical-takeoff precision cruise missile—and the company’s momentum has only accelerated since.

Today, the Gen Zer is running a company with six weapons programs, a 115,000-square-foot headquarters and manufacturing facility in Huntington Beach, California, and ambitions to build everything from airframes and jet engines to solid rocket motors, energetic systems, and autonomous technologies.

The company’s rapid growth comes amid a broader boom in defense tech. Allie reported earlier this year that a record $19.8 billion was deployed into the sector in the first quarter of 2026 alone. Thornton, however, is betting that Mach can do more than simply ride that wave. After several years spent developing and testing its technology, the company is now shifting its focus toward production. 

“For a company like Mach, private capital lets us take risk earlier. We can build before there’s a massive program behind something, test it, learn from it and change it quickly,” Thornton told Fortune. “And because we think about manufacturing from the beginning, we’re not designing something and figuring out how to produce it years later. We’re building the product and the production capability at the same time.”

Turning teenage military interests into a defense tech unicorn

Thornton’s interest in defense started well before Mach—and before he was old enough to drive a car.

Growing up in a military family in Texas, Thornton increasingly became concerned about China’s rise and what he described as an “impending great power conflict.” By 16, he was already prototyping defense applications on his parents’ property, experimenting with hydrogen-powered weapons using materials sourced from Home Depot and Amazon.

He took that interest to MIT, where he studied aerospace (and even made the football roster) while working with the school’s federally funded defense research center, Lincoln Laboratory. Before finishing his first year, Thornton received a Thiel Fellowship and left MIT to focus full-time on his company.

Mach quickly caught the attention of Silicon Valley. In June 2023, Sequoia Capital led a $5.7 million funding round in Mach—the VC’s first investment in a hardware defense technology company. Stephanie Zhan, a Sequoia partner who led the investment, summed up Thornton’s ambitions at the time:

“Ethan is a force of nature: from his technical depth and genuine obsession with the problem to his bias for action and maturity beyond his years,” Zhan said. “Defense technology is central to our safety and security, and Mach is a step-function advancement to the state of the industry.”

For Thornton, however, the lessons from building Mach so young have been less about having all the answers than about knowing who to surround himself with.

“Find people who are better than you at the things you don’t know, who will challenge you and who believe in what you’re trying to build,” he said.

Thornton’s core advice for other young people with ambitious ideas is similarly straightforward: Don’t be afraid to fail.

“You have to be willing to learn as you go, make mistakes and keep moving. Have conviction in the problem you’re trying to solve, and then surround yourself with people who can help you solve it.”

Preston Fore
X: @forepreston
Email: preston.fore@fortune.com

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This story was originally featured on Fortune.com