Following the death of Theodosius I in 395 and the permanent division of the Roman Empire between his two sons, the city, which would popularly come to be known as Constantinople, became the capital of the Eastern Roman Empire.
This empire, which would later be branded by historians as the Byzantine Empire, ruled most of the territory of present-day Turkey until the Late Middle Ages; although the eastern regions remained in firm Sasanian hands up to the first half of the seventh century.
Mount Nemrut, built by Antiochus I of the Armenian kingdom of Commagene, is notable for its summit where a number of large statues are erected around what is assumed to be a royal tomb from the 1st century BC.
In 324, Constantine I chose Byzantium to be the new capital of the Roman Empire, renaming it New Rome.
However, the Byzantines later began using this name to define the Seljuk-controlled parts of Anatolia in the centuries that followed the Battle of Manzikert in 1071.
The first state that was called Armenia by neighbouring peoples was the state of the Armenian Orontid dynasty, which included parts of eastern Turkey beginning in the 6th century BC.Turkey is bordered by eight countries with Greece and Bulgaria to the northwest; Georgia to the northeast; Armenia, the Azerbaijan and Iran to the east; and Iraq and Syria to the south.The country is encircled by seas on three sides with the Aegean Sea to the west, the Black Sea to the north, and the Mediterranean Sea to the south.The name of Turkey (Turkish: Türkiye) can be divided into two components: the ethnonym Türk and the abstract suffix –iye meaning "owner", "land of" or "related to" (originally derived from the Greek and Latin suffixes –ia in Tourkia (Τουρκία) and Turchia).The first recorded use of the term "Türk" or "Türük" as an autonym is contained in the Old Turkic inscriptions of the Göktürks (Celestial Turks) of Central Asia (c. An early form of the same name may be reflected in the form of "tie-le" (鐵勒) or "tu-jue" (突厥), name given by the Chinese to the people living south of the Altay Mountains of Central Asia as early as 177 BC.The House of Seljuk was a branch of the Kınık Oğuz Turks who resided on the periphery of the Muslim world, in the Yabgu Khaganate of the Oğuz confederacy, to the north of the Caspian and Aral Seas, in the 9th century.In the latter half of the 11th century, the Seljuk Turks began penetrating into medieval Armenia and the eastern regions of Anatolia.Turkey is a secular, unitary, formerly parliamentary republic which adopted a presidential system with a referendum in 2017; the new system came into effect with the presidential election in 2018.Turkey's current administration headed by president Recep Tayyip Erdoğan of the AKP has enacted measures to increase the influence of Islam, reversed and undermined Kemalist policies, and has reversed earlier reforms such as freedom of the press.The Bosphorus, the Sea of Marmara, and the Dardanelles, which together form the Turkish Straits, divide Thrace and Anatolia and separate Europe and Asia.From the end of the 13th century the Ottomans started uniting these Turkish principalities in Anatolia and then went on to create an empire that encompassed much of Southeast Europe, West Asia and North Africa.