There are a gazillion ways for a civilization or a world to defend itself.
The choice of method tells us a lot about the civilization, how they think, what they value.
A truly peace loving civilization, for example, might defend itself by building strong partnerships with other civilizations. They are less likely to be attacked because they have friends or they ARE friends. In a disagreement, their first response will be to send a negotiator. Partnerships will be valued and celebrated. They might even recognize the special celebrations of their partners as well as their own.
A war loving, violent civilization, as another example, might defend itself by attacking first. They will have a strong military with many of its residents expected to serve or have served in it. There will be multiple holidays or celebrations of the military. They will place special emphasis on wars in their history, maybe even reenacting them.
Adding these details can add richness to your world and/or your story!
