International investment treaties accord foreign investors and their investments protection from unlawful encroachments by state authorities as well as violence by third parties. From the perspective of investors, this protection becomes especially relevant in times of armed conflict. For states, however, such times make the provision of this protection especially difficult. Arbitral proceedings in the aftermath of the so-called Arab Spring have laid bare unresolved issues and posed new challenges arising from the factual and legal implications of armed conflict. At the same time, international investment law is deeply rooted in issues of war and peace. Not only the first arbitration based on a modern bilateral investment treaty but also the historical precursors of international arbitration have touched upon armed violence and the treatment of aliens. This Introduction presents the themes of the book and provides an initial overview of the relevant legal framework and employed methodology.