Christianity came into being in the Jewish community in Palestine in the 1 century. Before the end of the first century, it gradually developed to Syria, Egypt and Asia Minor, and extended to Greece and Italy. Christianity was persecuted until the 4th century, when Constantine the Great of the Roman Empire issued the decree of Milan, declaring it a legitimate religion. In 380, Theodosius I declared Christianity the state religion of the Roman Empire. Everyone should believe it.