The First Council of Constantinople was held in 381 AD and was the second ecumenical council of the Christian Church. It aimed to address various theological disputes, particularly those related to the nature of the Holy Spirit and the ongoing conflict with Arianism, a belief that denied the full divinity of Jesus Christ. The council reaffirmed the Nicene Creed, expanding it to include a clearer statement about the Holy Spirit. The council was convened by Emperor Theodosius I and included bishops from across the Roman Empire. It played a crucial role in shaping early Christian doctrine and established the authority of the Bishop of Constantinople, further solidifying the city's importance in the Christian world.