Casus belli

Casus belli is a Latin term that means "cause for war." Imagine that you're playing a game with your friends, and one friend takes your favorite toy without asking. This might make you angry and want to fight with them. In the grown-up world, countries sometimes get angry with each other and want to go to war, and casus belli is the reason they use to justify it.

For example, if one country believes that another country is causing harm to their citizens or violating their rights, they might use this as their casus belli to declare war. It's like saying, "They did something really bad to us, so we have to fight them to protect ourselves."

However, countries can't just declare war for any reason they want. There are laws and rules in place, and they have to have a valid casus belli to justify going to war. It's like if you were playing a game with your friends, you can't just hit them for any reason. If they broke the rules of the game, that might be a valid reason to do something about it.

So, the idea of casus belli is basically to have a good reason for starting a war, rather than just fighting because you feel like it. It's important because war can be very dangerous and destructive, and it's important to think carefully before starting one.