It is said that the first Ottomans are actually a late coming Turkish clan which had moved from middle-Asia to Anatolia in the leadership of Ertugrul Gazi.
As tradition has it, on crossing the Central Anatolian Plateau, Ertughrul one day spied a cloud of dust on the horizon. It had risen from the battle near Eskisehir – formerly Dorylaion – which a Seljuk detachment was fighting against Mongol invaders. Ertughrul took an historic decision, although probably
unaware of what its consequences would be. He resolved to intervene in the battle,
thus enabling the apparently losing side to win. That day the Ottomans saved the
Empire of Rum.
To show his gratitude, the Seljuk Sultan Kaihusrev II (Kaikosrau) gave Ertughrul a strip of land encircling the battlefield. The land extended from Eskisehir along the Sakarya (in antiquity: Sangarios) Valley. It corresponded roughly with the Roman province of Bithynia which the Seljuks had taken from the
Byzantines about a century previously.
One night while Osman Gazi (the son of Ertugrul Gazi) was staying over at Seyh Edebali’s dergah whom was his mentor, he had seen a dream. A light coming from Seyh Edebali’s chest was going into his own chest and a tree was raising from his there.The tree’s branches was covering the whole world, people was walking under them, rivers were running. In the morning he asked the seyh about this dream. And the seyh told him that he’s going to be a Bey (Lord) and there will be lots of sultans from his sons, that they will gather a lot of countries between the same borders.
That was the dream which was settled in Osman Gazi’s mind for years. In a short time later he became a Bey after retiring of his father (Ertugrul Gazi) and founded his own feudal state in 1299 in a small town called “Sogut”.
Osman I founded a small empire there, which he called “Memalik Osmanya”, or “The Principality of Osman”. He made Bursa its capital in 1305, captured Gemlik in 1326 and thus laid the foundations of what was to become the Ottoman Empire.