“For the weapons of our warfare are not of the flesh but have divine power to destroy strongholds” (v4). Paul didn’t have an army or even a large institution to back up his correction of the Corinthians. He wasn’t battling against the sinful world, but against lies and false beliefs inside the church. Paul depended on the “divine power” of the Holy Spirit to do battle for the souls and minds of the Corinthian believers, who were being led astray by “arguments and lofty opinions” (v5).
Our minds are most difficult battleground we will ever face. We are called “to take every thought captive to obey Christ” (v5), by the power of the Spirit.