The Bible gives several descriptions of angels in military terms, such as their encampment (Genesis 32:1-2), command structure (Psalms 91:11-12; Matt.13:41; Rev.7:2), and combat (Jdg.5:20; Job 19:12; Rev.12:7). The heavenly host participated in the War in Heaven.
In the Book of Joshua 5:13-15, Joshua encounters a “captain of the host of the Lord” in the early days of his campaigns in the Promised Land. This unnamed heavenly messenger is sent by God to encourage Joshua in the upcoming claiming of the Promised Land:
Once when Joshua was near Jericho, he looked up and saw a man standing before him with a drawn sword in his hand. Joshua went to him and said to him, ‘Are you one of us, or one of our adversaries?’ He replied, ‘Neither; but as commander of the army of the Lord I have now come.’ And Joshua fell on his face to the earth and worshiped, and he said to him, ‘What do you command your servant, my Lord?’ The commander of the army of the Lord said to Joshua, ‘Remove the sandals from your feet, for the place where you stand is holy.’ And Joshua did so. — Joshua 5:13-15 (NRSV)
In the English epic poem Paradise Lost by John Milton, the Archangel Michael commands the army of angels loyal to God against the fallen angels of Satan. Armed with a sword from God’s armory, he bests Satan in personal combat, wounding his side.