Operation Koronis (Greek: Επιχείρηση «Κορωνίς», "crown" in Greek) was a military campaign launched by royalist government in Athens against the main stronghold of the communist forces during the Greek Civil War. The communist defenses were two lines of fortifications with minefields and concealed bunkers. Initial air attacks used small-sized bombs and inaccurate targeting, but eventually the frequency of attacks was more than tripled. After neutralizing the minefields by forcing herds of animals to walk over them, the government army launched simultaneous attacks from two sides. In the southwest, the hill of Kleftis changed hands repeatedly. With heavier casualties against a numerically superior opponent, the communists had their wounded and artillery moved across the border to the People'