What is the use of scripture to justify the use of force?

In the Old Testament, you have an abundance of Scripture that demonstrates how God empowered and blessed in Israel in the context of her military exploits. Genesis 14 has Abraham taking 318 men against the combined forces of four hostile kings. He's able to defeat them and is blessed for his actions. The conquest of the Promised Land has Israel accomplishing some amazing military victories. So much so that even those that were not in Israel's crosshairs felt obligated to attack her just because they were that intimidated (see Numbers 31 [Midian wasn't too be harassed, yet Midian sought to destroy Israel and God worked through Israel in a way that resulted in a crushing defeat for the Midianites]). Joshua 12 lists all of the defeated kings that Israel destroyed in the context of military force. Judges 3:1-2 shows how God allowed some nations to endure in order to teach the skill of warfare to Israel.

In the New Testament, Jesus admonished His disciples to get a sWord and if they don't have one, to go buy one. Some will insist that this is figurative and that the sWord being referred to is the SWord of the Spirit (aka the Word of God). But that doesn't make sense in light of the fact that if Jesus was referring to Scripture rather than an actual weapon, then He's telling the disciples to go buy a Bible which doesn't make sense. In addition, the role of Christ in the New Testament was not military in nature. Just like He didn't get married because He wasn't here to start a family, He didn't fight with traditional weapons because He wasn't here to lead a revolution. He was here to defeat the power of sin which meant a different approach. But the same God Who hung on the cross is the same God that inspired and empowered the armies of Israel in the Old Testament. It is the same God Who David refers to in Psalm 18:34 where He says that it is God Who trains his hands for battle.

So the use of force is common in Scripture, but it is to always be done under the heading of being obedient to God. What defines military action as being either noble or ruthless is the motive behind it. Provided you're taking your cue from Christ and you're laboring to defeat evil, you're doing a good thing.