A King's Gambit — A.J. Cooper

The cities of Eloesus are warring among themselves, as they have since the beginning. Locked in mistrust and rivalry, they fail to see the most powerful empire in the world setting the gears of invasion into motion. The King of Kings, padisha emperor of Fharas, has made his move to swallow them whole.
Theron, hero of the city of Thénai, can only see a slim hope in an impossible task: uniting the fatally divided cities under one banner. No one has ever succeeded before.
The second book of the Wind of Destiny series.