According to the way I heard it, this happened during World War One.
One day Mr. Ouspensky was walking down a street in St. Petersburg when he saw a truck driving by on its way to the front. The truck was filled with artificial legs. These legs were not for solders who had already had their limbs blown off, but were for those that would inevitability have legs blown off in the coming battles.
At that moment Ouspensky realized that all the people fighting were "asleep", in a sort of waking trance, and that they would mechanically follow the orders of their officers and charge out against the enemy and be blown up.
He further realized that if all the solders woke up from their trance, that everyone would lay down their arms and go home to their families.
At that moment he was enlightened.
Divide in yourself the mechanical from the conscious, see how little there is of the conscious, how seldom it works, and how strong is the mechanical - mechanical attitudes, mechanical intentions, mechanical thoughts, mechanical desires. PD Ouspensky