Since up to 98 percent of the population are Muslims, Christians are a minority religion in Turkey. Because it is a secular country, the only Muslim country in the world that has no State religion, the Constitution guarantees religious freedom, and tolerance is the rule. The population includes members of the Armenian Apostolic and Greek Orthodox churches, Roman and Eastern Catholics, and Jews. Today, approximately 120,000 Christians and 26,000 Jews live in Turkey, out of almost 80 million of the total population.
After the crucifixion of Jesus Christ, many of the early Christians, escaping from persecutions in Jerusalem, came to Asia Minor and settled in different cities like Ephesus, Hierapolis and Cappadocia. St. Paul preached in Perge, Konya, Derbe, Lystra, Psidian Antioch and Ephesus, where he wrote his Letter to Ephesians). St. John stayed for a while in Ephesus together with Virgin Mary and, after he returned from Patmos where he was exiled, died in Ephesus. St. Peter settled in Antioch and build the first Christian church carved in a cave. St. Philip settled in Hierapolis but was murdered together his family by the Romans.
Christianity was declared as the official religion in 380 AD, during the reign of Theodosius I, and destruction of pagan temples was legalized. Even so, throughout the Byzantine era Christianity had great ups and downs in popularity. Many found the road to piety confusing and assorted schisms between the Roman Catholic church and the Orthodox Byzantine church certainly didn't simplify matters. During the Ottoman period the "Dhimmi" tax was implemented, taking 50 percent of earnings from non-Muslims as opposed to a small amount from Muslim believers. The result was that large numbers of peasants converted their faith to Islam. Islam was also a relatively simple path to follow - profess belief in One God and the mission of Prophet Muhammed, and follow the Five Pillars of Faith.
Gradually, Christianity in Anatolia disintegrated, so that when the Islamic Ottomans finally conquered the Byzantine Empire, it was inevitable that what had been a predominantly Christian region would be no more.