Napoleon reportedly said that a good sketch is better than a long speech. This might make him the first practitioner of model based system engineering. MBSE is an approach to system engineering where document based communication is exchanged for building a domain model. This is typically done through graphical languages like UML or SysML. A model gives us the opportunity to query it, run tests against it and verify it's validity. This talk will demonstrate how a model can be built with Gaphor and how it's integration with the wider Python ecosystem can help us to prevent mistakes. It won't prevent you from attempting to invade the Russian Empire in wintertime but it will help you make sure your system architecture is sane.