2 Corinthians 10:4
(For the weapons of our warfare [are] not carnal, but mighty through God to the pulling down of strong holds;)
Note 7 at 2Co 10:4: One of the main weapons that Paul was speaking of is the Gospel, the sword of the Spirit, which is the Word of God. It's the Word backed by God's Spirit that can pull down and crush the strongholds of Satan. Notice that Paul used the word "weapons" in the plural, referring to many spiritual weapons. The following is a partial list of scriptures that speak of some of the weapons of God: Ge 3:24; Jos 5:13; Nu 22:23, 31; 1Ch 21:16; Jdg 7:20; Jer 50:25; Ro 13:12; 2Co 6:7; Eph 6:10-18; 1Th 5:8; Re 1:16, 2:12, and 19:15.
Note 8 at 2Co 10:4: Every Christian is at war. There is a perpetual struggle against Satan and his kingdom from which there are no "leaves" or "discharges." The Enemy goes about as a roaring lion, seeking whom he may devour (1Pe 5:8). Those who resist the devil will see him flee (Jas 4:7). The only ones whom he devours are those who don't actively fight against him.
The kingdom of heaven is under attack (Mt 11:12), and only those who become militant in their resolve will enjoy the spoils that are ours through Christ (see note 2 at Mt 11:12).