Who is Stephen Hubbard, imprisoned American released by Russia?

Russia released retired American teacher Stephen Hubbard on Wednesday after nearly five years in detention. Hubbard was serving a seven-year sentence following accusations by prosecutors that he worked as a mercenary for Ukraine during the Russian invasion. President Trump announced the release on Truth Social, following confirmation from U.S. special envoy Steve Witkoff. This development occurs amidst an apparent warming of diplomatic ties between Washington and Moscow, ending Hubbard's imprisonment in the Russian Federation.