Patriarch Alexius I of Constantinople served as the spiritual leader of the Eastern Orthodox Church from 1948 until his death in 1972. He was known for his efforts to promote ecumenism and improve relations between the Eastern Orthodox Church and other Christian denominations. His tenure was marked by a commitment to social justice and the welfare of the faithful. During his leadership, Alexius I faced significant challenges, including the political tensions of the Cold War and the impact of modernity on religious life. He worked to address these issues while maintaining the traditions of the Byzantine Church. His legacy includes a focus on unity and dialogue within the Christian community.