Bilecik

i.The Hills Between Bursa and Eskişehir

Bilecik is a small province in the wooded hill country between Bursa to the west, Eskişehir to the south, and Sakarya to the north. The country is rugged but accessible — the upper Sakarya river runs through it from the southeast, the small Karasu river from the west, and the country is heavily forested with pine, oak, and the chestnut woods that gave the small town of Söğüt ("Willow") its medieval name. The provincial capital, Bilecik, sits on a rocky outcrop above the Karasu valley at 540 metres; Söğüt, 35 kilometres east, is at 670 metres on the western edge of the wider Anatolian plateau. The country is the natural land-bridge between the Marmara basin and the high plateau, and through it ran one of the principal east-west caravan routes of medieval Anatolia.

ii.Belekoma — the Byzantine Frontier Town

The historic-period town on the modern site of Bilecik was the Byzantine fortified centre the Greek sources call Belekoma (or Belakoma) — a small but well-defended hilltop city on the road from Nicaea (modern İznik) to the Anatolian plateau. The Byzantine sources of the 11th to 13th centuries describe it as a working frontier post on the southwestern face of the contracting empire's Anatolian territories. The country around it — Söğüt, Domaniç, İnegöl, Yarhisar, Karacahisar — was a mosaic of small Byzantine fortified centres facing the gradually advancing Turkmen population of the central plateau.

iii.Ertuğrul Gazi at Söğüt (1231–1281)

The decisive change came in 1231, when the Anatolian Seljuk sultan Alâeddin Keykubad I — campaigning against Byzantine raids on the Seljuk frontier — granted the small village of Söğüt and the adjacent summer pasture (yaylak) at Domaniç to the Turkmen chieftain Ertuğrul Bey, leader of the Kayı tribe and father of Osman, as reward for distinguished service in the campaign. The Valilik's official account records that the Kayı arrived at Söğüt from Central Asia "with four hundred tents."

For the next fifty years Ertuğrul Bey ruled the small Kayı emirate from Söğüt, raiding into Byzantine territory and gradually expanding his control over the surrounding hill country. He died in 1281 and was buried at Söğüt; the Ertuğrul Gazi Türbesi — the tomb-shrine, in its present form a rebuilding of 1886 under Abdülhamid II on the foundations of an earlier 14th-century structure — remains the most important historical site of the province.

iv.Osman Gazi and the Conquest of 1299

Ertuğrul Bey was succeeded by his son Osman Bey (Osman I, c. 1258–1326), the eponym of the Ottoman dynasty. Under Osman's leadership through the 1290s the Kayı emirate methodically captured the surrounding Byzantine hilltop towns: İnegöl (1283), Karacahisar (1288, made the first Ottoman judicial seat), Yarhisar, and finally Bilecik itself in 1299. The captured city was made the new political centre of the emirate, and Söğüt continued as the symbolic dynastic seat.

The conventional year 1299 — the year of the conquest of Bilecik, and traditionally the year of Osman's declaration of independence from the Anatolian Seljuk Sultanate — is the founding date of the Ottoman state, and the Republic of Türkiye observes it as such. The standard scholarly treatment is in Heath Lowry's The Nature of the Early Ottoman State (SUNY Press, 2003) and Cemal Kafadar's Between Two Worlds: The Construction of the Ottoman State (University of California Press, 1995).

v.The Founding of the Ottoman State

Bilecik served as the political and administrative centre of the early Ottoman emirate for the first quarter of the 14th century. From here Osman Gazi's forces extended their control westward toward the Marmara — taking Bursa in 1326 (the year of Osman's death) — and northward toward the Black Sea. The administrative centre of the dynasty moved to Bursa in 1326 with the conquest of that city, and from then Bilecik was a working sancak of the wider Ottoman Anatolian state rather than its capital.

The transition is preserved symbolically in the dynastic burials. Ertuğrul Gazi's tomb is at Söğüt in Bilecik province; Osman Gazi's tomb is at the citadel of Bursa; Orhan Gazi's tomb is beside his father's at Bursa. Söğüt-Bursa-İstanbul became the three successive dynastic capitals of the empire, marked by the three successive tomb-sites.

vi.The Ertuğrul Gazi Türbesi and the Söğüt Festival

The Ertuğrul Gazi tradition was substantially revived under Abdülhamid II in the late 19th century as part of the Hamidian programme of dynastic-historical commemoration. The current form of the Ertuğrul Gazi Türbesi dates to a Hamidian rebuilding of 1886; the annual Söğüt Ertuğrul Gazi'yi Anma ve Yörük Şenlikleri — the "Söğüt Festival for the Commemoration of Ertuğrul Gazi and the Yörük People" — was instituted in the same period and has been held continuously since. The festival, held annually in early September, draws large crowds to the Türbe and the small Söğüt town centre; it features re-enactments of the Kayı arrival and Ottoman early-period military displays.

vii.Ottoman Bilecik through the Centuries

Through the long Ottoman centuries Bilecik province was a working second-tier sancak in the Hüdavendigâr Eyaleti (the larger Bursa-centred province), with its principal industries the silk-and-mohair production of Bilecik town and the small-scale ceramics of the Söğüt-Bozüyük country. The province carried no special administrative status after the early-14th-century transition of the dynasty to Bursa, but the religious-and-symbolic importance of Söğüt was renewed periodically through the Ottoman centuries, particularly during the long Russo-Turkish frontier wars of the 19th century. The opening of the Haydarpaşa–Eskişehir railway in 1894 — which passed through Bilecik and Bozüyük — gave the province its first modern transport infrastructure.

viii.The Republic and the Modern Province

Republican Bilecik has been a small, quiet province. Its population through the 20th century has remained modest by Marmara standards — agriculture, light industry, the small-scale ceramics for which the province is still known. Under the TÜİK 2024 address-based registration count the province population is approximately 232,000; the metropolitan municipality covers eight districts. The two central districts are Bilecik Merkez (~82,000) and Bozüyük (~81,000) — the latter, the larger industrial centre on the Eskişehir-Bursa rail and motorway corridor, has grown rapidly through the 2000s with the Eti Holding, Erbosan, and other manufacturing investments. Söğüt itself remains a small market town of about 19,000, anchored by the Türbe and the annual festival.

The province is the seat of Bilecik Şeyh Edebali Üniversitesi (founded 2007, named for the spiritual mentor of Osman Gazi at the founding of the dynasty).

ix.What to See, in Order

The principal pilgrimage of the province is to Söğüt and the Ertuğrul Gazi Türbesi — the rebuilt 1886 tomb-shrine of the dynasty's founder-father, in a quiet hillside park above the small town centre. The adjoining Söğüt Müzesi (a small Ottoman-period museum) and the Ertuğrul Gazi Camii (1886, the Hamidian-period mosque commissioned alongside the Türbe rebuilding) complete the small Söğüt circuit. The other minor monumental site is the Şeyh Edebali Türbesi in Bilecik town centre — the tomb of the Anatolian-Sufi sheikh whose blessing (in the dream-vision tradition of the foundation narrative) confirmed Osman's rule over the dynastic line.

For the wider province, the historic Byzantine-period Belekoma Kalesi on the outcrop above Bilecik town gives the only standing trace of the pre-Ottoman city. The 12th-century Orhangazi Camii (1304, in Bilecik town centre) — built by Orhan Bey during his father's lifetime — is among the oldest standing Ottoman-period mosques in Türkiye. Bozüyük is the principal modern centre; its small Kasım Paşa Camii (1521) is a working Ottoman-period mosque.

The small hill country where Ertuğrul Gazi's Kayı tribe was given Söğüt in 1231 and where, two generations later, Osman Bey took Bilecik in 1299 — and the Ottoman state was founded.

For the first major Ottoman capital that succeeded Bilecik, see Bursa; for the city to its south where the Kayı winter-pasture lay, see Eskişehir. For the wider Marmara hill country in the wider sense, visit our sister site CountryOfTurkey.com.