NationStates

I am still getting used to this game. When it comes to national and international conflicts do you just make crap up or what, how does it work ?

There's no "declare war" button, so essentially yes. Think of it as group storytelling - the owners of two nations writing the story of their nations' war. As such, it's expected to follow some rules of continuity and realism, although what is required and how seriously said rules are taken varies from player to player. You can find a comprehensive list of guides and advice on the subject here: viewtopic.php?f=5&t=12342