At the onset of Russia's full-scale invasion of Ukraine in 2022, "Karl" was an officer responsible for combat and special training. During the defense of Mariupol, he participated in urban warfare as part of the Azov Regiment's reconnaissance group and was later involved in commanding an artillery-turned-infantry unit. Karl endured Russian captivity and was exchanged in September 2022. After his release, he became head of Azov's training section. From February to May 2024, he commanded a battalion tactical group fighting near Terny, where his unit destroyed significant numbers of enemy personnel and equipment. In January 2025, he was appointed commander of the newly established International Battalion.