The Bible sometimes refers to the people of God in military terminology (Ephesians 6:11–17, 2 Timothy 2:3, etc.). We are the army of the Lord, called into service to do battle with Satan. Our purpose, with Christ as our leader, is to defeat the devil's efforts to lead us and others away from God. There can be no greater or more worthwhile task given to those who serve God.
Historically, people have been inducted into the military either by being drafted or by volunteering. But in the spiritual army of God, there is no such thing as forced conscription. People willingly choose to become soldiers in this army. They do so out of a desire to serve God and others; they do so with a spirit of joy and thankfulness rather than one of dread. Oh, there may be a degree of uncertainty — the literal fear of God may help move them — but, in every sense of the term, it is a personal, freely made decision. This is the very nature of faith, the basic factor in our response to God's call.
That same spirit of volunteerism continues to characterize the life of God's devoted soldiers for the rest of their lives. Someone might object that God gives us commands, which we must obey. This is true, both for those wanting to enter the Lord's army and for those wishing to continue in his service. But a primary emphasis is the willful nature of the choice we make in obedience. "Endure hardship" is as much a command as is "repent and be immersed." Another might point to Paul's reference to our relationship to Christ as "slaves" (Romans 6:16ff). The context, however, shows that spiritual slavery, "whether ... to sin, which leads to death, or to obedience, which leads to righteousness," is a willing acceptance of that slavery, one in which we "offer" ourselves as slaves to our chosen master.
Because of the volunteer nature of the army of God, it naturally follows that without a spirit of willing volunteerism (is there any other kind?), the army will be hampered in its efforts to move forward. Soldiers in human armies can be forced to move, if necessary, but God's troops move voluntarily, even while under the command of Jehovah. This is why it is so important for us to be willing to follow where Jesus leads in the fight against Satan.
When soldiers rebel against authority or insist on a selfish pursuit of personal activities and goals, the army of God is hampered, and the devil wins. When we are unwilling to volunteer our resources and use them in the service of our king, we show our contempt for the glory of God and the souls of others.
The final victory of God over Satan has been foreseen — it is sure. But our part in it, and that of those we influence, depends on our willingness to faithfully fulfill our commitment, made when we volunteered for service in God's army.