The chapter explores the challenges related to the conduct of operations and the preparations for such operations as regards implementing international humanitarian law and international human rights law, exploring some of the differences between the two systems. In particular, the concepts of necessity and proportionality are examined, as well as the right to life and issues related to capture and detention, and the different meanings of those concepts and their scope in each of the two paradigms. As regards international humanitarian law, the chapter also discusses a number of challenges to interoperability in multinational military operations. The discussion on international human rights law, on the other hand, focuses on the inherent challenges in implementing that body of law in the context of (multinational) military operations outside a nation’s own borders.