This article discusses the criteria for establishing the beginning of an occupation. To this end, it analyzes the wording and drafting history of IHL instruments as well as international case law. It also looks at the influence of human rights law, in particular the notion of “jurisdiction” as used in the ICCPR and the ECHR, on the concept of occupation. Given that the IHL instruments on occupation were drafted some time ago, the impact of a number of technological developments in military affairs on the criteria for the beginning of occupation are discussed. The article concludes that the core of the concept of occupation consists of a negative and a positive element. The negative element is that the indigenous authorities of the occupied territory have been rendered incapable of functioning publicly. The positive element is expressed in Article 42 of the Hague Regulations as the requirement that the territory ‘is actually placed under the authority of the hostile army’.