Terrorism: Attempt to get one's way in politics or religion by violence and murder.
Very many religious and political groups have indulged in terrorism, if given the chance, though the perpetrators of terrorism almost always call it by a different name, such as "fight for freedom", "guerilla", "righteousness of the faithful", or "Holy War".
One of the functions of the state is to protect its population from terrorism, which often happens by denying the population the right to bear arms. The great danger of states is that state-terrorism has been by far the most dangerous and succesful form of terrorism: Hundreds of millions of individual human beings were murdered in the 20th C alone by state-terrorism. (Fascism, Communism).
The normal effect of terrorists who oppose some state - including those merely called so by organs of state security - is to increase the powers and practices of state-terrorism in order "to fight terrorism".
Since the state organs are, outside police states, quite incapable of adequately dealing with terrorism, as indeed they should be, if one wants to avoid a totalitarian police-state, the only rational way to prevent the possibility that a small set of terrorists can enslave a large population is to allow and trust the average of that population sufficiently much to bear arms - as is the case in the U.S. and Switzerland, but in few other so-called "states of law".
In most of Europe, any civilian, however civilized - if not already famous from the media - is the effective inferior of any policeman, however uncivilized and inferior: The former must be unarmed and kowtow for his supposed rights to the latter, whose abuses and malpractices as a rule are covered up all the way to the top, including politicans and civil "servants".