However Petrobey's ultimate goal was the freedom of Greeks from Ottoman rule, and he used his local power and autonomy to build support for a large scale Greek rebellion. In 1821 this rebellion formally began in what would become the Greek War for Independence. He was known as a dealmaker and voluntarily ceded leadership of the rebellion to Theodoros Kolokotronis when it became politically necessary. He contributed vital contingents of troops to liberate Kalamata and Tripolis and participated in the expedition to help the Souliotes. On this expedition Petrobey's young brother Kyriakoulis Mavromichalis heroically died fighting the Turks. Under the leadership of Petrobey and his brother Konstantinos Mavromichalis, Greek forces successfully defeated renowned Ottoman commander Ibrahim Pasha during the Egyptian Invasion of Mani. This military victory secured Greek control of the strategically important city of Nafplio which, after the revolution, would become the first capital city of the modern Greek state.