Nicomedia

Nicomedia

French illustration of Nicomedia, 1882
Shown within Turkey Show map of Turkey Nicomedia (Sea of Marmara) Show map of Sea of Marmara
Location	Turkey
Region	İzmit, Kocaeli Province
Coordinates	40°45′45″N 29°55′03″E / 40.76250°N 29.91750°E / 40.76250; 29.91750

Nicomedia (/ˌnɪkəˈmiːdiə/;^[1] Greek: Νικομήδεια, Nikomedeia; modern İzmit) was an ancient Greek city located in what is now Turkey. In 286, Nicomedia became the eastern and most senior capital city of the Roman Empire (chosen by the emperor Diocletian who ruled in the east), a status which the city maintained during the Tetrarchy system (293–324).

The Tetrarchy ended with the Battle of Chrysopolis (Üsküdar) in 324, when Constantine defeated Licinius and became the sole emperor. In 330 Constantine chose for himself the nearby Byzantium (which was renamed Constantinople, modern Istanbul) as the new capital of the Roman Empire.

The city was incorporated into the Ottoman Empire with the victory of Sultan Orhan Gazi against the Byzantine Empire. The Byzantines managed to retake it in the aftermath of the Battle of Ankara, but it fell definitively to the Ottomans in 1419.