In the 1992 report ‘An Agenda for Peace’, the United Nations Secretary-General asserted that the ‘concept of peace is easy to grasp’. With regard to international peace operations, this assertion may have been true at the time: until the end of the Cold War, international peace operations were deployed to protect peace between States. However, since then such operations have undergone a significant normative transformation. Now, operations are also being deployed to protect or strengthen peace within States, and the mandates are developed to promote peace in a positive sense rather than only in the more ‘easy to grasp’ negative sense. The chapter analyses the mandates of UN authorised peace operations to clarify this evolution from a negative to a positive definition of peace in the context of peace operations. The chapter discusses the two-sided interaction between the concept of ‘peace’ and the applicable law, namely on the one hand whether a stronger and more coherent conceptualization of ‘peace’ can contribute to a strengthening of the legal regime applicable to peace operations, and on the other hand whether a stronger legal regime in turn can contribute to a more effective protection of the ‘peace’ that peace operations are ultimately intended to protect.