Among the foreign fighters heading to Ukraine to fight against Russia are dissidents from Belarus living in exile.
They see the war as a battle both against the forces of Vladimir Putin and against the regime of Belarusian President Alexander Lukashenko, who actively supports Moscow.
The BBC met Pavel Kulazhanka, who left his life in New York to join the fight.
Reporter: Mark Lowen
Camera: Francesco Tosto
Producer: Michael Steininger