NIKAO "to conquer"
"Ephesus hated the terrible deeds of the Nicolaitanes; Pergamos accepted them. Ephesus was troubled only with deeds--but by the time the deeds reached Pergamos, they became doctrine (Rev 2:15). Ephesus would not put up with the Nicolaitanes, but Pergamos held the corrupters to her bosom and permitted them to corrupt and poison the sources of purity and morality in the local assembly there."
(The Revelation Verse by Verse Study, Dr. Oliver B. Greene)
"Pergamum was the first city in Asia (AD 29) with a temple for the worship of Augustus (Octavius Caesar)...very center of emperor worship."
(Robertson Word Pictures)
See "The Two Babylons: The Great Red Dragon."