Gradually the ghazi lifestyle came to be based less on the idea of Holy War, as after 1348 peace was made with the Christians, and ghazis came to rely on trade and the settled institutions of the Saljuq hinterland. By the mid C14th there were 2 important centres of Levant trade at ancient Ephesus (Ayasolug) and Miletus (Balat), where Venetian consuls visited and wealthy Christian merchants settled; Italians bought such products from Anatolia as cotton, silks, rice, wheat, saffron, wax, wool, hemp, raisins, alum, valonia, slaves, tin and lead.

Such a settled life-style naturally led to the construction of buildings in which to house the infrastructure, creating the phenomenon of architecture, as an index of sedentary as opposed to nomadic lifestyle. In 1331 Orkhan Bey, the son and successor of Osman, opened a medrese in Iznik; having made Bursa his capital in 1326, a monastery there was converted to a medrese which housed a complex of buildings including a mosque, alms-house, baths and caravanserai, and he built a mosque in 1340 (Orkhan Cami, Bursa) which is recognised as one of the two most important works of architecture under the beys, showing a refined artistic taste though simpler in decoration than Saljuq monuments. Orkhan was also the first Ottoman to adopt the title Sultan.

Orkhan Ghazi became pre-eminent among the beys by capturing in quick succession the Byzantine fortresses of Bursa (1326), Iznik (1331) & Izmid (1337). After annexing the principality of Karasi in 1345, the Ottomans were facing Europe, and soon after this Orkhan married the daughter of the Byzantine emperor, John Cantacuzenus. In 1354 he concluded an agreement with the Genoese, thereby obtaining allies for his projected operations in the Hellespont; an earthquake destroyed the fortress of Gallipoli and others nearby, and the Ottomans immediately moved in and re-fortified them, establishing for themselves a permanent foothold in Europe.