His reign was initially peaceful, but he was eventually involved in a conflict with the Karamanids, which forced him to seek an alliance with the Ottoman state.

He arranged the marriage of his daughter Devletşah Hatun and Murad I's son and future successor, Bayezid.

Although he secured an alliance with the Ottomans, Germiyan lost considerable land as Suleiman left numerous towns and smaller settlements for them to seize, including the capital Kütahya, as part of the dowry payment.

Germiyan first appeared around Malatya in 1239 under Kaykhusraw II's rule of the Sultanate of Rum tasked to subdue Baba Ishak, and in 1277, they were involved in the fight against Jimri and Mehmed of Karaman in western Anatolia.

He sent the kadi of Bursa, Mehmed Efendi, emir-i alem Aksungur Agha, as well as their consorts, Chavushbashi Demirhan, and the nanny of Bayezid to Kütahya to formally request marriage with Suleiman's daughter.

[5][2] Apart from these towns, many smaller settlements were annexed by a force of 2–3,000 Ottoman troops escorting the wedding convoy.

Shaykh-oghlu has also authored a prose, Kanz al-kubarāʾ, and a verse romance, Khurshīdnāme, dedicated to Suleiman Shah.