Having been appointed commander-in-chief of the Ottoman forces in Epirus, he marched south, to meet the Greek forces under Alexandros Mavrokordatos, which were campaigning towards Arta. He inflicted a crushing defeat upon them in the Battle of Peta, on 4 July 1822, and proceeded southwards, to the strategically important town of Missolonghi. There he was met by Omer Vrioni, and their joint force of 8,000 besieged the city for two months, from 25 October to 31 December 1822. Omer Vrioni, contrary to Reşid Mehmed's view, initially tried to take the town by negotiations, which the besieged Greeks took advantage of, dragging them out until November 8, when they were reinforced by sea, at which point they refused to negotiate further. The siege began in earnest, and the two pashas scheduled their main assault for Christmas night, December 24, calculating that the Greeks would be caught by surprise. The plan was leaked to the defenders, and the attack failed. Six days later, the siege was lifted.