It gets very old hearing that Christianity is the cause of wars. If we define Christianity as any group of people who claim to follow Christ, the accusation may be true. But if we are talking about the actual followers of Christ the claim can never be true.
To follow Christ, the Prince of Peace, is to walk in His footsteps. It is to apply His teachings and the teachings of His apostles to every aspect of our lives. There is no excuse for the crusades and other political wars fought in the guise of Christianity by the ignorant and misguided. The Kingdom of God is enlarged by persuasion, not coercion. Christ-followers pray for their enemies and win them over by love, respect and service.
I am tempted to belabor this point with a bunch of scripture quotations (the source or our worldview as Christ-followers) but nearly everyone has access to the New Testament and can do their own searching.
You’ll find a lot of fighting in the Old Testament. These incidents, however, fall into the category of God-sanctioned punishment, defense and survival. Often, Israel was punished for disobedience (idolatry, debauchery, injustice, etc.) by infidel armies from surrounding nations. They were preceded by prophetic warnings. As they conquered Canaan, they were the instrument of punishment (Leviticus 18:24-28).
Don’t make the mistake of buying-in to the rant of those who parrot the nonsense they hear elsewhere. The teachings of Christ and His apostles comprise the only hope for peace in this fallen, war-torn world.