I will again quote Barnett Rubin. When he was here, he was asked whether it was possible to be successful in Afghanistan or whether the situation was desperate. Barnett Rubin, always quick with a comeback, immediately replied that it depended on what objectives had been set. I think that is the answer to your question.
Since 1956, lofty objectives were systematically set for peacekeeping operations, but the troops on the ground were not necessarily given the resources to fulfil those ambitions.