That depends on what you're trying to do. As an anarchist technique, it's a _sine_qua_non_ -- long experience with military matters shows that successful, reliable violence requires the construction of a strong government, especially in the long term. As a method for establishing a national state, that is, changing the ethnic category of your oppressors, it's probably not a very good idea. Perhaps it worked in India, but much smaller countries have managed to kick the British out using other means.