In 14th century, to the end of the period of Orhan Bey, Sultanönü was captured by Karamanoğulları. During period of I. Murat, son of Orhan Bey, this region became a question of power among them. When I. Murat ascended the throne, he decided to organize a military expedition to Rumeli. Taking the advantage of the opportunity, Karamanoğulları united their forces with Varsaks, Turguts, Türkmens and Sivas Governor against I. Murat. Sultan, having learned that plan, went back to Anatolia. He beat all of them and captured Ankara. While he was returning, he took Sultanönü in 1363 from Karamanoğulları. Borders of Ottomans reached to Karamanoğulları lands and at South to the North of Hamitoğulları State. When Germian Governor’s daughter Devlet Hatun was married to Sultan’s son Bayezid in 1381, control of the Northwest part of Germian State was passed to Ottomans.

In early years of Ottoman State, names of Seyitgazi or Sivrihisar did not appear especially in entries about battles, because conquests were towards to Byzantium, Northwest for early years. Seyitgazi was pronounced to be an important center for Bektaşizm for this period.

On the other hand, Sivrihisar was inside the borders of Karamanoğulları State in first half of 14th century. It was added to Ottomans’ lands after the military expedition to Ankara by I. Murat.

While Ankara Battle in 1402, as Sultan Yıldırım Bayezid was beaten by Timur Han, who was willing to end Ottomans’ sovereignty, gave Sivhisar and many other regions to Karamanoğulları to strengthen other states. It is said that Timur had settled his headquarters in Sivrihisar for a while. After Yıldırım Beyazid died, Sivrihisar had passed to Ottomans’ control again.

At the end of 15th century, the struggle among II. Bayezid and Cem Sultan had resulted in important events in Eskişehir, or i.e. Sultanönü region. Cem Sultan, who rushed into Bursa in 1481, beat Ayaş Paşa’s army sent by II. Bayezid. After that II.Bayezid attacked to Bursa and beat Cem Sultan. Cem Sultan escaped to Eskişehir firstly and then went to Konya. He reached to Egypt in 1482.

In 16th century, Eskişehir gained importance according to its location. There is an interesting document that reached to us from Ottoman Empire in 16th century. The document includes pictures of miniature art, belonging to different centers of population, by Matrakçı Nasuh. He had participated Iran military expedition with Kanuni Sultan Süleyman.

In that age, talents about geometry, mathematics, history, military, battle tactics was called as “MATRAK”. His works left to present time are two books of mathematics, six books of history one of which is a translation about battle and army. In his books, there are also miniature pictures demonstrating Ottoman Army and battle strategies he told about.

Until early years of Faith’s governance, Eskişehir was a village under the control of Ankara State and then Kütahya State for 1451-1831. Eskişehir was governed by colonels between years 1451-1831 and then became a city bounded to “Hüdavendigar” (Bursa) State in 1841. Eskişehir won its own identity as a province merely in 1925.

Eskişehir public started to feel the movement especially in economy created by railways in new age. The advantage of carriage of agricultural products and other raw materials had arisen. In addition beginning with the construction of railway here, new work places were opened. The population of Eskişehir had risen by immigrants in early 20th century and the appearance and social structure of the city had changed. After the great fire happened in Aşağı District in 1905, marketplace and its surround burned out ad the city had to be reconstructed.