first country to adopt christianity as state religion
Armenians Most Armenians adhere to the Armenian Apostolic Church, a non-Chalcedonian church, which is also the world's oldest national church. Christianity began to spread in Armenia soon after Jesus' death, due to the efforts of two of his apostles, St. Thaddeus and St. Bartholomew.[26] In the early 4th century, the Kingdom of Armenia became the first state to adopt Christianity as a state religion.[27]
Early centers of Christianity Thessaloniki, the major northern Greek city where it is believed Christianity was founded by Paul, thus an Apostolic See, and the surrounding regions of Macedonia, Western and Eastern Thrace, and Epirus, which also extend into the neighboring Balkan states of Albania and Bulgaria, were early centers of Christianity. Of note are Paul's Epistles to the Thessalonians and to Philippi, which is often considered the first contact of Christianity with Europe.[38] The Apostolic Father Polycarp wrote a letter to the Philippians, c.125.