I need help with what this quote means by Mahatma Gandhi?

"Nonviolence is the greatest force at the disposal of mankind. It is mightier than the mightiest weapon of destruction devised by the ingenuity of man." Thats the quote which is said by Mahatma Gandhi or Mohandas Gandhi. I'm not quite sure what this means. See I'm entering a contest in my state and I was wondering if someone(s) would be able to help with what this means. Please answer back ASAP :). Thanks!!