PRZEMYSL, Poland — Every night at Przemysl’s graceful 19th-century train station, there is a line of people stepping off packed carriages, fleeing Russia’s invasion of Ukraine. But every night at this same train station, there is also a line of people going the other way: into war. As the skies darkened over Przemysl on Sunday, Chris, an American military veteran, stood with a bunch of burly men, scarves pulled up over their faces, guarding a small mountain of camouflage backpacks stuffed with bandages, chest seals, Kevlar helmets, bulletproof plates and other hush-hush gear.
Next to him was Andrii Shapur, a young Ukrainian who had been living in Poland, working as a carpenter, and was now itching for action on the front lines.
His reason for going?
“Obligation,” Mr. Shapur said simply.
In front of them, sounding calm without a shred of doubt, waited Zhanna Koloshova.
“If it comes to that, I’m ready to fight,” said Ms. Koloshova, with a fierce look in her blue eyes, just a shade darker than her overcoat.
She was returning from Brussels, where she had left her two children under the care of her brother, freeing her up to focus on the war effort.
“Of course I’m scared, it’s only natural,” said Ms. Koloshova, a travel agency owner from western Ukraine, her voice trembling for the first time. “But this is our country, and this is our war.”
“They came to our land. They brought death upon us,” Ms. Koloshova said of the Russian Army, holding firmly to a backpack, her only luggage.
Behind all of them paced Alex Povstyan, a highly educated 53-year-old biophysics researcher in Leeds, England, who felt an overwhelming urge to drop everything and go home to serve.
The windswept borderlands of Poland and Ukraine are flooded with hundreds of thousands of Ukrainian refugees, mostly women and children, who have spent days escaping the escalating conflict.
As the refugees step off the trains, many from Lviv in western Ukraine, they trudge down a ramp right in front of the smaller group of people eager, each for his or her own reasons, to go the other way.
Chris, the American military veteran, who asked that his last name not be used because he plans to join an international combat brigade, said he had been looking for a cause to join and this one seemed the most inviting.
“The doors were wide open,” he said. “The Ukrainians were saying they needed help. And there’s safety in numbers.”
“If I was trying to get to Mali,” he said,