At the Review Conference on the International Criminal Court’s Rome Statute, States Parties achieved a significant and historic result. They adopted, by consensus, a definition of the crime of aggression and conditions for the exercise of its jurisdiction for purposes of the International Criminal Court (ICC). While not all States were completely satisfied with the final outcome—some desiring a stronger jurisdictional regime, others desiring only Security Council referrals, and others disagreeing with the amendment process—activation of the ICC‘s crime of aggression jurisdiction in 2017 or thereafter has significant potential to change State practice with regard to use of force, and certainly the development of international criminal law. This Chapter provides an overview of the negotiations leading to the Review Conference. It then discusses key features of the amendment adopted in Kampala, including the definition of the crime, the conditions for the ICC’s exercise of jurisdiction over the crime, the elements of the crime, and certain understandings; it also discusses the crime’s jurisdictional reach once the ICC can exercise jurisdiction. The Chapter concludes with suggestions how commencement of jurisdiction in 2017 or thereafter could impact State decisions regarding use of force as well as the ICC’s docket.