For though we walk in the flesh, we are not waging war according to the flesh. For the weapons of our warfare are not of the flesh but have divine power to destroy strongholds. We destroy arguments and every lofty opinion raised against the knowledge of God, and take every thought captive to obey Christ, being ready to punish every disobedience, when your obedience is complete.  (2 Corinthians 10:3-6)

Paul identifies ‘strongholds’ – the Greek is ὀχύρωμα ochuróma, literally ‘fortress’ –  which means conceptually and in context, ‘a place of refuge from reality’; in other words, Paul is speaking about inner desires, wishes, dreams and fantasies, alongside any other idolatrous and rebellious notions to which the follower of Christ may cleave.  These are inner and personal fastnesses that resist the Holy Spirit, and he says that the individual is to seek them out in themselves and tear them down.