After the Council of Basel/Ferrara/Florence ended in 1445, the East and West churches were nominally unified. Metropolitan Isidore of Kiev had been funded by Vasili II to go to the conference, even though Vasili II wasn't as convinced of the need for an alliance with the West as Isidore. When Isidore returned, he was promptly arrested, and the union with Rome denounced. But... why? I can understand why the people and clergy in Constantinople resented the union, but what did Moscow have to gain from remaining with the doomed Byzantines? If anything, they could also have used strengthened ties with Western powers, as they were in an ongoing struggle with the Tatars. It seems like the Pope and Isidore both expected Vasili to comply; why didn't he just adopt the Latin rite? And what would have happened if he had?