This article surveys the prosecution of acts constituting grave breaches of the Geneva Conventions in national courts. In these national prosecutions, international criminal law is not always applied in a uniform manner. Acts constituting grave breaches are not only prosecuted as such, but are also charged as other international crimes (like crimes against humanity or genocide) or ordinary crimes, like murder. The author argues that a divergent national application of international criminal law is not necessarily problematic but can (within the limits posed by international law) be a useful and important motor for the development of the law. A survey of national case law demonstrates the potential of the grave breaches regime to ensure universality of punishment for these war crimes, and also reveals that the grave breaches regime has so far not lived up to its potential.