 The failure of their expedition has been attributed to Pawnee opposition, combined with the difficulty of maintaining a force of that size on the country with no supply lines.The Pike party arrived at the Guide Rock village on September 25, 1806, a few weeks after Melgares's departure, and remained there for nearly two weeks.While there, Pike persuaded the Pawnee to haul down the Spanish flag that they had been given by Melgares, and to replace it with an American flag.