Musar zu Jehoschua 7:2

And if trouble comes, such as famine, plague or other catastrophes, let him always worry lest his sins caused these events — for Achan trespassed in the matter of the dedicated spoils and several thousand Israelites fell because of his fault (Jos. 7:2-22) — and let him return to God, Blessed be He, according to his ability.

Of course, their attitude could not be described as pious, although Joshua had acted in a similar fashion prior to the capture of Ai (Joshua 7,2). The difference was that Joshua would not forego the command of G–d just because there were what appeared to be insurmountable natural difficulties. It was not in order for instance, to inquire which route should be taken, since up to now, G–d's pillar of cloud had taken care of that chore, and they had never sent a spy to show them the way in the desert. Even the matter of mountains and valleys was something that the Israelites in the desert did not need to concern themselves with, since the pillar of cloud made their route level, regardless.