Deuteronomy - Chapter 20

In this chapter we see God as a warrior.  When the people go to war they are not to be afraid, even if the enemy seems greater then them.  The reason is given in verse 4:

Do not let your heart faint, do not be afraid, and do not tremble or be terrified because of them; for the Lord your God is He who goes with you, to fight for you against your enemies, to save you.

People often refer to the Jesus in the New Testament as "meek and mild".  Yet in the book of Revelation we see that Jesus is also shown as a warrior.  Chapter 19 says:

"Then I saw heaven opened, and a white horse was standing there. Its rider was named Faithful and True, for he judges fairly and wages a righteous war. His eyes were like flames of fire, and on his head were many crowns. A name was written on him that no one understood except himself. He wore a robe dipped in blood, and his title was the Word of God. The armies of heaven, dressed in the finest of pure white linen, followed him on white horses. From his mouth came a sharp sword to strike down the nations. He will rule them with an iron rod. He will release the fierce wrath of God, the Almighty, like juice flowing from a winepress. On his robe at his thigh was written this title: King of all kings and Lord of all lords."