Summary: To be ready for battle we need to be properly clothed.
The passage begins by informing us to be strong in the Lord and in the power of His might. How do we accomplish this? The next verse instructs us to put on the whole armor of God.
The battle Paul lays out for us is immense. It is not against flesh and blood, it is a spiritual battle of great proportion. Consider the battles of Paul’s day to gain an understanding of this battle. In Paul’s day, opposing foot soldiers faced off against each other on the field of battle. At the rear of the soldiers was the generals who oversaw and directed the battle, leading the fight through messengers and signals such as flags, hand signs and horns. Now each person in the battle fought in their own way, there were foot soldiers, archers, horsemen, messengers and generals. The ultimate goal for each foot soldier was the opposing general, but their immediate preoccupation in the battle was the opposing soldiers coming against them.
We are foot soldiers in God’s army. Our ultimate enemy, the general calling the shots on the opposing site is Satan, and under his command are territorial spirits, but we are more likely to have spears thrown at us by his foot soldiers, low level demons, and so to deal with these attacks, we need, in Paul’s words in 2 Corinthians 10:4 (quickview) , "divine power to demolish strongholds." That is why putting on the whole armor of God is important. It is not Satan who is picking people off in the battle, but his low level foot soldiers who press the battle against us, taking unprepared, and unarmed Christians captive along with those without the knowledge of Jesus Christ. It is time to rise up in the battle and take back the land the devil has stolen, it is a day for a call to arms.
So lets prepare ourselves tonight with an understanding of the weapons of our warfare. The first piece is the belt of truth. In the Roman armor, a girdle was a belt which would hold his tunic tight so he might be free with his movements, it also provided a place for the soldier to hand his sword. The imagery here is that truth holds together all other virtues, making them effective. Putting on God’s truth means living out his word, being honest and sincere in our faith. It refers to Christian character and integrity, a lifestyle that conforms to the Scripture.
Paul tells us then to put on the breastplate of righteousness. The purpose of the breastplate is to guard the most vital organs of your body, it is the bullet proof vest that protects the heart. Righteousness is the first gift of God that was given us through the Cross, where our sins are covered by the blood and God sees us as righteous. It is the first condition of the heart, the heart which controls the course of our lives. When we put on the breastplate of righteousness, we acknowledge our need to remain free from sin.
After the breastplate, Paul says to shod your feet with the preparation of the gospel of peace. The caligal, the Roman military boot, was one of the most important parts of their equipment. They were designed for long marches over every kind of rough terrain. In fact, it has been said the soldiers boots were the secret of the Roman conquest.