Eastern Orthodox theology is the study of the beliefs, teachings, and traditions that belong to the Eastern Orthodox Church. This church is a major Christian church, and is rooted in the religion of the Ancient Greeks, who adapted the Hebrew Bible and shared their understanding of Christianity with other Christians during the Byzantine Empire.
In the 20th century, Eastern Orthodox theology and the Eastern Orthodox Church experienced several new developments. During World War I, the Russian Empire suffered under communist rule and was drastically altered, meaning the Russian Orthodox Church had to suffer as well. As a result, there was a significant decrease in the number of members and priests of the Russian Orthodox Church in the early 20th century.
The mid-20th century was a time of growth for the Eastern Orthodox Church. Numerous churches that had abandoned Orthodox Christianity during the 17th and 18th centuries returned back to Eastern Orthodoxy. This period is known as the Second Great Schism in which many Christians who had been part of the Protestant Reformation returned to the Church's traditional practices.
In the late 20th century, Eastern Orthodox theology became more prominent and accepted. This was due in part to the fall of Communism in the Soviet Union along with an increase of immigration of Orthodox refugees from the Middle East and East Europe to the West. The Orthodox Church began to spread its teachings and traditions to new places and populations, influencing a variety of Christian practices around the world.
Today, the Eastern Orthodox Church is now considered one of the largest Christian churches in the world, and continues to grow as more people join the faith and learn Eastern Orthodox theology.