Around 1498, Joseph Bolharynovich, Metropolitan of Kiev, and Wojciech Tabor, Bishop of Vilnius, attempted to persuade Helena to support a church union as it was envisioned at the Council of Florence – the Orthodoxs would retain their traditions, but would accept the pope as their spiritual sovereign. Helena refused, but Ivan III used it as one of "casus belli" when he renewed the war with Lithuania in May 1500. At the time Poland, Lithuania's ally, was engaged in the Polish–Ottoman War (1484–1504) and could not offer assistance. The Muscovite army scored victories in the Battles of Vedrosha and Mstislavl and captured several Lithuanian fortresses.