Putting the garrison at Kaskaskia in charge of a Captain Williams, Clark devoted his time to these treaties, which, he says, "were probably conducted in a way different from any other known in America at that time." The custom had been to conciliate the savages with a great display of presents, thus assuming a suing attitude and was often constructed as fear. Aside from the fact that he had no presents to give, that was not Clark's policy. He met them with the lordly demeanor of a conqueror, and while he observed the elaborate ceremonies so dear to the savage heart, he kept his ascendancy at every turn of the diplomatic game. His blunt directness and his fairness had their effect, and his perfect fearlessness - a trait that is respected above all others by the Indian - made him master of the situation. An instance may be cited to illustrate this. Cahokia was full of Indians from at least a dozen different tribes, and Clark privately confesses that he was "under some apprehension among such a number of devils," but if so, the "Devils" never knew it. Soon after his arrival one of the bands laid plans to murder his guards and carry him off bodily, and the attempt, or its first motion, rather, was actually made in the dead of night, but was frustrated by his vigilance. The town was stirred up and some of the conspirators caught. Clark, assuming an air of indifference, simply said that, as they had disturbed the peace of the place, the townsmen could do with them as they saw fit, but privately he directed that the chiefs of the band be arrested and put in irons; which was done by the French inhabitants, thus proving their new allegiance. Thus manacled, these chief were brought to the council day after day, but not permitted to speak. Finally, their irons were taken off and Clark condescended to say to them that, though their conduct deserved death, yet he regarded them as "only old women, too mean to be killed by the 'Big Knives'." He told them that so long as they remained they should be treated as squaws, and when they were ready to go home, provisions would be given them, as women did not know how to hunt; with which he turned from them with contemptuous indifference. This drastic humiliation was, perhaps, the most scathing punishment that could be visited upon an Indian brave, and the agitated chiefs tried to approach him with a speech and a pipe of peace, but he declined to hear them, broke the pipe and told them that "the 'Big Knife' never treated with women, and for them to sit down … and not be afraid."

The next move astonished even Clark. After a "most lamentable speech," two young braves of the band were offered to be put to death as atonement for the guilt of all. Of this incident Clark quaintly says: "It would have surprised you to have seen how submissively those two young men presented themselves for death, advancing into the middle of the floor, sitting down by each other and covering their heads with their blankets to receive the tomahawk. … This stroke prejudiced me in their favor, and for a few moments I was so agitated that I don't doubt but that I should, without reflection, have killed the first man that would have offered to have hurt them" (Letter to Mason).

The upshot of this was quite on a par with the poetical justice usually observed in fiction. Clark ordered the two heroic young warriors to rise, greeted them as men, and then and there conferred on both of them the degree of chief, presented them as such to the French and some Spanish gentlemen who were present, and had the garrison salute them.

Following the attempt to kidnap Clark, and while the effect upon the other Indians was yet uncertain, he simulated the utmost indifference to danger, remaining in his lodgings away form the fort, apparently without guard, though really with fifty armed men concealed in the building, and even assembling a number of the citizens for a dance the night following the disturbance (Clark's letter to Mason). The result of it all was a vast increase of prestige, and his reputation as a great chief spread far and wide.

During these treaties at Cahokia, which continued through the month of September, 1778, an "amazing number of savages," as Clark expresses it, attended, some of them coming a distance of five hundred miles, and in his letter to Mason, as many as ten tribes are specified besides others included in a general reference.