 Greece 's mountainous terrain favored a defensive strategy and the high ranges of the Rhodope , Epirus , Pindus and Olympus mountains offered many defensive opportunities . However , air power was required to protect defending ground forces from entrapment in the many defiles . Although an invading force from Albania could be stopped by a relatively small number of troops positioned in the high Pindus mountains , the northeastern part of the country was difficult to defend against an attack from the north . 
