Mitropetrovas was initiated into the Friendly Society in 1819. He took part in the War of Independence by the side of Theodoros Kolokotronis to whom he was fiercely loyal. In 1821, he took part in the siege of Kalamata, the siege of Tripolis and the Battle of Valtetsi. In 1824, he was jailed in Hydra, as a loyal Kolokotronis supporter, during the infighting that broke out among the Greeks. On May 18, 1825, Kolokotronis and all his supporters - including Mitropetrovas - were released to fight the threat from Ibrahim pasha and his Egyptian force who were sent to quell the war of independence. Mitropetrovas took part in the battles of Drambala, Trikorfa, Karyes and Dragomano. In 1826 he fought at his native Garantza.