Every professing Christian is the soldier of Christ. He is bound by his baptism to fight Christ’s battle against sin, the world and the devil.
The man that does not do this breaks his vow. He is a spiritual defaulter. He does not fulfill the engagements made for him. The man that does not do this is practically renouncing his Christianity. The very fact that he belongs to a church, attends a Christian place of worship, and calls himself a Christian, is a public declaration that he desires to be reckoned a soldier of Jesus Christ.