The 'terrorist' attacks on parts of USA/America on 11th September 2001 were used as an 'excuse'/'legitimization'(sic.) to launch the 'war on terror' - during which the U.S., U.K., and 'allies', have themselves used 'weapons of mass destruction' against large numbers of fellow human beings.
Hundred of thousands of people have died, been physically or psychologically maimed, or otherwise 'terrorized' by these state powers in the name of this 'war on terror'.
At, more or less, the 'same time', the very non-state 'terror' forces these state powers claim to oppose have had their ['claimed'] 'legitimacy' enhanced by the escalation of ['claimed'] 'grievances'.
Meanwhile, in the name of 'war on terror', the USA, U.K., and 'allies' - including other NATO 'powers' - have 'intervened' in [essentially] 'civil wars' in Libya, Syria, and other places, in such ways that the 'war on terror'/ 'war of conquest' now seems to have spread to Africa ... and beyond ...