Of all the independent states in the Carpathians, Wallachia is the youngest. It was conceived in the mind of a voivode named Basarab, who decided to renounce his allegiance to the Hungarian King.
The King, of course, didn't accept this. He sent his army to crush Basarab's rebellion. But – much to the King's surprise – it was his army that got crushed at Posada, in AD 1330.
After this humiliating defeat, the King continued to demand Basarab's loyalty, but to no avail. And so Wallachia became independent.