Ostroh (; ) is a historic city located in Rivne Oblast (province) of western Ukraine, on the Horyn River. Ostroh is the administrative center of the Ostroh Raion (district). Administratively, Ostroh is incorporated as a city of oblast significance and does not belong to the raion. Population: The Ostroh Academy was established here in 1576, the first higher educational institution in modern Ukraine. Furthermore, in the 16th century, the first East Slavic books, notably the Ostrog Bible, were printed there. History The Hypatian Codex first mentions Ostroh in 1100, as a fortress of the Volhynian princes. Since the 14th century, it was the seat of the powerful Ostrogski princely family, who developed their town into a great centre of learning and commerce. Upon the family's demise in the 17th century, Ostroh passed to the Zasławski and then Lubomirski families. In the second half of the 14th century, Ostroh, together with the whole of Volhynia, was administratively integrated into the Grand Duchy of Lithuania. Following the Union of Lublin (1569), the town became part of the Crown of the Kingdom of Poland, where it remained until the late 18th century (see Partitions of Poland). Ostroh, known in Polish as Ostróg, received Magdeburg rights in 1585. In the 17th century, the town was surrounded by fortifications, with a moat, a rampart with five bastions. In 1609–1753, it was the capital of the Ostrogski family fee tail, founded by Voivode Janusz Ostrogski, who invited Bernardine monks to Ostróg. Furthermore, the town had a Calvinist academy; among its lecturers was Andrzej Wegierski. During the Khmelnytsky Uprising, the town was torched by the Cossacks, and its Jewish residents were brutally murdered. The Great Maharsha Synagogue, built in 1627, was damaged during this period. Ostróg slowly recovered, and in the second half of the 18th century, it became the site of a Jesuit college (see Collegium Nobilium). In 1793, the town was forcibly annexed by the Russian Empire, where it remained until 1918. Railroad lines, built in the 19th century, missed Ostróg, and as a result, the town stagnated. The railway station serving the area was built in 1873, 14km away, in the village of Ożenin. In the interbellum period, Ostróg belonged to the County of Zdołbunów, Volhynian Voivodeship of the Second Polish Republic. It was an important garrison town for the Polish Army, and the Border Protection Corps (KOP). The KOP Battalion "Ostróg" was stationed