Abstract: Today, most warfare is conducted with and through partners. As of March 2017, for example, the U.S. State Department identified 68 States and international institutions that formed the coalition against the Islamic State of Iraq and Syria (ISIS). In every partnership, each member brings its own legal interpretations, policy priorities, and military capabilities. Reconciling these disparate elements often poses significant difficulties, not least for legal advisors. While partnered warfare is by no means a recent invention, it is nonetheless vital that, in order to protect civilians, those who may be involved in or otherwise affected by such operations understand relevant risks and challenges. This one-session case study zooms in on one of the pivotal decision points in contemporary partnered conflicts: whether or not to share intelligence with a partner. With a focus on managing legal responsibility and protecting civilians, participants are primed to quickly weigh countervailing considerations, navigate interoperability challenges, and make strategic decisions in high-pressure, time-sensitive, complex operations involving several States and non-state armed groups. While fictionalized, the simulation exercise — which involves a growing threat from a designated terrorist group to a civilian population and several States — draws from experiences of recent diverse coalition operations. This case study’s general background document acquaints participants with foundations of the law and highlights ways to manage risk. The other case materials provide information about the simulation exercise’s setting as well as instructions for each of the simulation exercise’s six partners.