This chapter examines the meaning of a ‘use of force’ under article 2(4) of the UN Charter, focusing on its required effects, gravity and intention. It analyses the required type of effects, namely, whether they must be physical, the required object/target, the required level of directness between the act and its harmful effects, and if temporary or potential effects count. With respect to gravity, it argues there is no de minimis threshold for a ‘use of force’ under article 2(4) but that gravity is nonetheless relevant to the contextual requirement that the act be in ‘international relations’ and is an indicative element of a ‘use of force’. Finally, it analyses whether a particular intention is required for a ‘use of force’ under article 2(4), examining accident, mistake and coercive and hostile intent. This section considers the relationship between the prohibitions of the ‘threat’ and ‘use’ of force, the non-intervention principle and the object and purpose of article 2(4). It concludes that like gravity, a coercive or hostile intent is relevant to the contextual requirements of article 2(4) and is an indicative element of a ‘use of force’.