(NewsNation) — Ukraine is four months into a war against Russia that experts say could last for years. The time comes with heart wrenching stories from war-ravaged areas.

Amid the heartbreak, one American scientist who was being hunted by Russians fortunately has a story of survival, thanks to a group of veterans from Florida.

John Spor is a Texas-based nuclear physicist with specific expertise in laser-guided weapons systems credited for designing highly classified U.S. military technology. He was based in eastern Mariupol when Russia invaded.

In May, the city of Mariupol surrendered to Russian forces after two months of bitter fighting. Spor fled after the siege, but he was reportedly hunted by Chechen Russians for months, even having his home ransacked. Amid what seemed like an endless artillery shelling while trapped behind enemy lines, Spor carefully went off the grid and into hiding.

While Spor was on the run and unable to escape Ukraine, his sister reached out to a number of people pleading for help to evacuate her brother, including the State Department, Sen. Ted Cruz and U.S. Rep. Randy Weber. They urged her to speak with Project Dynamo, since Spor is considered a high value target due to his intimate knowledge of U.S. military technology.

Project Dynamo believes if Spor were to be captured by Russians and interrogated, that knowledge could cause grave damage to U.S. and NATO forces.

“He was in a bad spot, and he’s a hard case. Everyone knows John. Everyone knows what he does, what he looks like,” Project Dynamo co-founder Brian Stern said. “Everyone knows that he’s American, which under normal circumstances is just fine. Within the context of the war, that’s a pretty hard nut to crack from an extraction perspective.”

Still, the group of veterans knew what they had to do.

More than 2,000 people in war-torn and Russian-occupied areas of Ukraine have been rescued by the nonprofit, made up completely of volunteers. Project Dynamo is currently looking at 15 potential rescue operations of people trapped in the war zone.

“We did a whole bunch of different things to establish secure communication, reliable communication, and then started directing him to do things that we needed him to do,” Stern explained. “Then ultimately, we got him into a safe house and then we started movement.”

The Project Dynamo team bravely hid John Spor and crossed more than 30 Russian checkpoints for around 20-30 hours, heavily relying on their years of military and security service training.

“It was 20 hours just in Ukraine. There was another 10 hours or so inside a Russian-occupied territory. It’s a war zone, and there’s everything that a war zone has. People die out here every single day,” Stern said. “There’s artillery, missiles, all kinds of things. The vast majority of Ukraine and our route was relatively safe, but there’s many, many, many checkpoints. Each one of those checkpoints could have been very perilous for John, so we went through 20 hours together. They were all very dangerous.”

Stern says they had to take different actions to mask Spor’s identity.

“He could not cross as an American. If you have an American passport in Russian-occupied Ukraine, you’re a spy. Just because. A simple Google search of him would have yielded his sensitive military technology career, so that couldn’t happen. We had to do all kinds of things to shield” Spor, Stern said.

Once near the border and in a safer area of Ukraine, the team confronted their Ukrainian driver to make sure he was not a Russian agent who infiltrated their operation. That’s when Stern swiftly moved Spor into a different van and whisked him out of the country.

Wednesday afternoon, Spor made it to safety. After months of uncertainty, the physicist was finally reunited with his sister who fought to bring him back.

Spor is now on his way from Poland to another nearby country, to be reunited with even more of his family.