KYIV — His severe wounds will no doubt alter the course of his life, but the 19-year-old Ukrainian paratrooper has no regrets about the part he played in the surprise and dramatic cross-border incursion into Russia’s Kursk region launched in mid-August.

Like his brothers in arms, he felt exhilarated when the order to attack came crackling along the radio airwaves as the sun rose. Here was the chance to hit back at Russia. “I felt myself a part of history, because it was the first time since the Second World War Russia’s been invaded,” Sergei, the flaxen-haired trooper, told POLITICO, who granted him permission to use a pseudonym as he is not allowed to speak to media.