 When the Greek War of Independence broke out in 1821 he immediately joined the rebels' ranks, and alongside Nikolaos Stournaras scored a number of early successes against the Ottoman forces in Thessaly.Hatzipetros served throughout the war, serving both in Central Greece and the Peloponnese under Kitsos Tzavellas and Georgios Karaiskakis, fighting with particular distinction in the battles of Neokastron and Arachova.Under Ioannis Kapodistrias, he was named a chiliarch, and under King Otto of Greece commander of the Royal Phalanx (a corps of veteran fighters of the War of Independence) of Eastern Greece.