When Leo died in 912, he was succeeded by his younger brother Alexander, who recalled Nicholas Mystikos and expelled Zoe from the palace. Shortly before his death, Alexander provoked a war with Bulgaria. She returned upon Alexander's death in 913, but Nicholas forced her to enter the convent of St. Euphemia in Constantinople after obtaining the promise of the senate and the clergy not to accept her as empress. However, Nicholas' unpopular concessions to the Bulgarians later in the same year weakened his position and in 914 Zoe was able to overthrow Nicholas and replace him as regent. Nicholas was allowed to remain patriarch after reluctantly recognizing her as empress.