At the start of the Russian invasion of Ukraine, in February 2022, he held the rank of major and was stationed in Mariupol, serving with the 36th Separate Marine Brigade.

Shortly after reaching Azovstal, Volynskyi released a joint statement along with Lieutenant Colonel Denys Prokopenko, commander of the Azov Regiment, vowing to fight on.

[1][2] During the siege of Azovstal, the last remaining Ukrainian stronghold within Mariupol, Volynskyi repeatedly made appeals for the evacuation of the wounded soldiers and civilians who had taken refuge in the plant.

[5] On 8 May, after the civilians had been evacuated, he once again asked "that a higher power find a way to figure out our rescue", stating "it feels like I've landed in a hellish reality show in which us soldiers fight for our lives and the whole world watches this interesting episode.

"[6] On 20 May 2022, Volynskyi surrendered to the Russian forces along with the last defenders of the Azovstal steel plant, marking the end of the battle for Mariupol after nearly three months.