This research is on the challenges that the state parties faced in including the crime of aggression under the international affairsfuture challenges that might arise in prosecuting the crime of aggression. The crime of aggression, formerly known as crimes against peace, is the use of unlawful force by a state against another state. Its prohibition started before World War One but successful prosecutions for this crime took place after World War Two when Nazi and Japanese leaders were prosecuted by the Allied Powers. The research will analyse some important international criminal law principles that will affect the laws prohibiting aggression since it is an international crime that has to be bound by principles already adopted and received by the international community. The biggest obstacle that the state parties had to overcome was an accepted definition of the crime for purposes of the Rome Statute. A definition was adopted in 2010 at the Kampala Review Conference but at least 30 states parties need to ratify these adoptions that will be reviewed again in 2017. The ICC will only have jurisdiction over this crime if enough ratifications are obtained from the state parties. Other challenges include: personal jurisdiction (who the ICC may prosecute for this crime); the leadership nature of this crime; the exclusion of non-state actors from the definition of this crime; immunity of state leaders that will further complicate their prosecution if responsible for committing aggression; the inclusion of humanitarian intervention as aggression; and the application of the principle of complementarity with regard to the crime of aggression. States, particularly the United States of America, have objected to the inclusion of this crime in the Rome Statute for fear that its nationals (military and political leaders) will be held criminally liable for making political decisions to use military force against another state. Current international affairs will be used to demonstrate why this crime has been difficult to prosecute compared to the other international crimes. After raising the challenges that the ICC might face I am going to offer possible solutions and recommendations that the ICC should first implement to be able to have more successful prosecutions of the crime of aggression.