More recently, Ronald Reagan and others in the American administration frequently called the mujaheddin "freedom fighters" during the Soviet–Afghan War, however twenty years later, when a new generation of Afghan men (militant groups like the Taliban and allies) were fighting against what they perceive to be a regime installed by foreign powers, their attacks were labelled terrorism by George W. Bush.Groups accused of terrorism understandably prefer terms reflecting legitimate military or ideological action. Leading terrorism researcher Professor Martin Rudner, director of the Canadian Centre of Intelligence and Security Studies at Ottawas Carleton University, defines "terrorist acts" as unlawful attacks for political or other ideological goals, and said:

There is the famous statement: One mans terrorist is another mans freedom fighter. But that is grossly misleading. It assesses the validity of the cause when terrorism is an act. One can have a perfectly beautiful cause and yet if one commits terrorist acts, it is terrorism regardless. Some groups, when involved in a "liberation" struggle, have been called "terrorists" by the Western governments or media. Later, these same persons, as leaders of the liberated nations, are called "statesmen" by similar organizations. Two examples of this phenomenon are the Nobel Peace Prize laureates Menachem Begin and Nelson Mandela. WikiLeaks editor Julian Assange has been called a "terrorist" by Sarah Palin and Joe Biden.Sometimes, states that are close allies, for reasons of history, culture and politics, can disagree over whether members of a certain organization are terrorists.
This dilemma, some social theorists would conclude, may very well play into the initial plans of the acting terrorist(s); namely, to delegitimize the state and cause a systematic shift towards anarchy via the accumulation of negative sentiments towards the state system. Religious terrorism
According to the Global Terrorism Index by the University of Maryland, College Park, religious extremism has overtaken national separatism and become the main driver of terrorist attacks around the world. Since 9/11 there has been a five-fold increase in deaths from terrorist attacks. The majority of incidents over the past several years can be tied to groups with a religious agenda. Before 2000, it was nationalist separatist terrorist organizations such as the IRA and Chechen rebels who were behind the most attacks. The number of incidents from nationalist separatist groups has remained relatively stable in the years since while religious extremism has grown. The prevalence of Islamist groups in Iraq, Afghanistan, Pakistan, Nigeria and Syria is the main driver behind these trends.Five of the terrorist groups that have been most active since 2001 are Hamas, Boko Haram, al-Qaeda, the Taliban and ISIL. These groups have been most active in Iraq, Afghanistan, Pakistan, Nigeria and Syria. Eighty percent of all deaths from terrorism occurred in one of these five countries. In 2015 four Islamic extremist groups were responsible for 74% of all deaths from Islamic terrorism: ISIS, Boko Haram, the Taliban, and al-Qaeda, according to the Global Terrorism Index 2016.