Hailing from the distinguished Cretan Kallergis family, he studied medicine at Paris and on the outbreak of the War of Greek Independence went to the Morea and joined the insurgents. He fought under Georgios Karaiskakis, was taken prisoner by the Turks before Athens and mulcted of an ear; later he acted as aide de camp to the French philhellene Colonel Fabvier and to Count Capo d'Istria, Governor of Greece.
In 1832 he was promoted lieutenant-colonel. In 1843, as commander of a cavalry division, he was the prime mover in the 3 September Revolution, which forced King Otto to dismiss his Bavarian ministers and grant a constitution. He was appointed military commandant of Athens, promoted to Major General and aide de camp to the king, but after the fall of the Alexandros Mavrokordatos ministry in 1845 was forced to go into exile, and spent several years in London, where he became an intimate of Prince Louis Napoleon.
In 1848 he made an abortive descent on the Greek coast, in the hope of revolutionizing the kingdom. He was captured, but soon released and, after a stay in the island of Zante, went to Paris (1853). At the instance of the Western Powers he was recalled on the outbreak of the Crimean War and appointed minister of war in the reconstituted Mavrokordatos cabinet (1854). He was, however, disliked by King Otto and his consort, and in October 1855 was forced to resign.
In 1861 he was appointed minister plenipotentiary in Paris, in which capacity he took an important part in the negotiations which followed the fall of the Bavarian dynasty and led to the accession of Prince George of Denmark to the Greek throne.
He died in Athens.
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.