Kolettis was born in Syrrako, Epirus and played a leading role in the political life of the Greek state in the 1830s and 1840s. Ioannis Kolettis studied medicine in Pisa, Italy and was influenced by the Carbonari movement and started planning his return to Epirus in order to participate in Greece's independence struggles.
In 1813, he settled at Ioannina, where he served as a doctor and after gaining standing he was recruited as the personal doctor of Ali Pasa's son, Muctar Pasa. He remained in Ioannina till March of 1821, when he entered Filiki Eteria and left for Syrrako, together with chieftain Raggos, in order to spread the revolution into the Rumelia, but his efforts quickly failed because of the rapid reaction of the Ottoman army. Kolettis was the leader of the pro-French party and based his power on his relations with the leaders of Rumeli but also on his ability to eliminate his adversaries by acting behind the scenes.
Greek War of Independence:
In the First Greek National Assembly, at Epidavros, he patricipated as the representative of Epirus and in January, 1822 he became Minister of Internal Affairs. After the Second Greek National Assembly, at Astros in May, 1823 he was appointed Euboea's sub-prefect and managed to remove Turkish troops off the island. At the same time, he continued his political activities, resulting in his election as member of the Supreme Government (Νομοτεστικόν), a position that he held till 1826.
At the end of 1824, during the Greek civil war of the revolution, he was in charge of Roumeli's (Central Greece) party and defeated the Peloponnesian party, which opposed the Kountouriotis government. Nonetheless, in the Third Greek National Assembly, he supported the Peloponnesian party and with its support was assigned to train troops from Thessaly and Macedonia, with the aim of destroying Ottoman resource depots at Atalanti. However, the whole operation failed because of his inexperience in military affairs, which ruined his reputation.
Political career after 1821 :
When John Capodistria landed at Nafplio in January 1828 as Governor, he was appointed as governor of Samos and later, on July, 1829 as Minister of Defense. In October of 1831, Capodistria was assassinated; in the ensuing civil war, which lasted until 1832, Kolettis was once again leader of the Roumeliot Party. He tried, along with Theodoros Kolokotronis and Augustinos Kapodistrias to form a government but due to severe disagreements the coalition was dissolved.
Political career under Otto of Greece's rule:
Until Otto of Greece reached adulthood, Kolettis was Minister of the Navy and Minister of Defense. In 1835, he was sent to France as the ambassador where he created connections with French politicians and intellectuals. He returned to Greece after the coup that broke out in Athens in September 1843, which forced King Otto to grant a constitution and Kolettis took part in the subsequent Constitutional Assembly. To contest the elections in 1844, he formed a party, the French Party (Γαλλικό Κόμμα) and together with Andreas Metaxas, leader of the English Party formed a government. When Metaxas resigned, he became Prime Minister and served as such until his death in 1847. He is credited with conceiving the Megali Idea or "Great Idea" which became the core of Greek foreign policy until the early 20th century.