What does "Asia" mean in Paul's writings?

Les explains that in Paul's terminology, Asia was the western half of Turkey as we know it, the area where Paul established so many churches. He identifies Ephesus, Thyatira, Pergamos, Derbe, Lystra, and Antioch of Pisidia as all being in what Scripture calls Asia or Asia Minor. Paul writes that all they in Asia had turned away from him, and Les notes that Phagellus and Hermogenes were the leaders. Les says this means all the congregations Paul founded in his gospel of grace and in the knowledge of the mysteries had now turned aside. He finds it heart-wrenching that after years of privation Paul had to reach that conclusion. Les is amazed that but for the grace of God Christianity would never have gotten off the ground, because it was constantly under satanic attack. He adds that even today the fundamentals of Christianity are under constant attack from within Christendom and from without.