In autumn 1805 he led the troops of the Greek Legion to participate in the Anglo-Russian invasion of Naples, alongside 14,000 Russian and 10,000 British troops. The expedition was cut short, however, by Napoleon's decisive victory at the Battle of Austerlitz in December. In February 1806, the Anglo-Russians were forced to abandon the Italian mainland to the French. In 1806 he commanded the Russian forces operating at the Bay of Kotor. He particularly distinguished himself in the capture of Castelnuovo on 19 September 1806, after a seven-hour battle. In late 1806 he was named colonel-in-chief of the . Taking command of the regiment and all the Greek troops in the Ionian Islands, he successfully countered the threat of Ali Pasha of Ioannina. He established three legions at the mainland outpost of Parga in 1807, and organized the defences at Lefkada (Santa Maura), threatened by Ali Pasha with attack.