Following the 9/11 attack, the world entered in to a global fight against terrorist organizations and state sponsoring terrorism. The fight has started in 2001 in Afghanistan against Al-Qaeda and Taliban and later extended to Iraq in 2003. However, the creation of the Islamic state (ISIS) and other terrorist organizations shifted both terrorism and the fight against terrorism to a different level. As a result, the world is under Global Fight against International Terrorism (GFIT). The GFIT has posed so many problems in the application of the rules of International Humanitarian Law (IHL). Therefore, this thesis is all about identifying the changes and ana-lyzing them pursuant to the rules of IHL. Accordingly, the thesis discusses about the absence of a generally, if not universally accepted definition of terrorism. Secondly, the challenge in classification of GFIT as an International Armed Conflict (IAC) or Non-International Armed Conflict (NIAC) and its impact on the applicability of rules of IHL. Thirdly, the thesis deals with the challenge of GFIT on the notion of direct participation in hostilities. And finally, the violations of basic principles of IHL will be discussed.