Tennis Star Sergiy Stakhovsky Leaves Wife, 3 Young Kids to Defend Ukraine

Ukrainian tennis star Sergiy Stakhovsky is back in Ukraine, voluntarily returning to defend his homeland against Russia -- and his second mission is making his wife understand why he's chosen to do the first.

Sergiy was in Kyiv Thursday when he joined us on "TMZ Live" ... and explained the extremely difficult decision he's made to leave his wife and 3 young kids -- ages 3, 6 and 7 -- in Hungary while he takes up arms in Ukraine.

As you can imagine, telling his wife he was leaving safety to go to the middle of his war-torn country was not easy ... and you can hear the agony in Sergiy's voice.

Sergiy says his wife was mad when he told her he was going back to Ukraine ... but he understood there would be no way she could understand.

He says things were initially extremely icy between them, but they are communicating again, and now he's just hoping he'll be able to ask for her forgiveness one day ... in person.

You wanna talk about being torn in separate directions -- Sergiy tells us he's not sure he made the right choice in joining Ukraine's reserve army, but at the same time he says staying home with his family in Hungary wouldn't be the right choice either.

This is just a few powerful moments of our conversation with him -- but Sergiy also told us how he and other Ukrainians are feeling about the possibility of a ceasefire, and about Vladimir Putin.