from http://www.britannica.com/bps/additionalcontent/18/22865568/The-Tword-Conceptualising-terrorism [emphasis mine]
“Gerasim Romanenenko, who emphasised that terrorism was both humanitarian and effective. It cost infinitely fewer victims than a mass struggle; in a popular uprising, the people' were killed while the real villains looked on from the sidelines. Terrorism, on the other hand, could be directed against the main culprits. To this Russian writer of the late 1800s, terrorism represented an application of modern science to the revolutionary struggle.9 In spite of justifications and theories underpinning revolutionary terrorism, Marxists disapprovingly referred to it as individual terror’. Karl Marx and Friedrich Engels often conflated the concept with force or violence in general. Marx stated that revolutionary terrorism was the only solution to shorten the “agonies of the old society and the birth pangs of the new”.10 The debate on terrorism among Russian Marxists flared up when the Socialist Revolutionaries became involved in terrorist activities around the turn of the century. Like Marx and Engels, Lenin was rather ambivalent in his views on `individual terrorism’.”
from http://en.wikiquote.org/wiki/Karl_Marx [emphasis mine]
We are ruthless and ask no quarter from you. When our turn comes we shall not disguise our terrorism.
- Marx-Engels Gesamt-Ausgabe, vol. vi pp 503-5