Despite several early victories, Price was ultimately defeated at the Battle of Westport by Union forces under Major General Samuel R. Curtis in late October.

He suffered further reverses at the hands of Union cavalry under Major General Alfred Pleasonton at the Battle of Mine Creek, Kansas, forcing him to retreat back into Arkansas.

The Union controlled the key western rivers and cities, Sherman was moving through Georgia, and Lee was tied down to the defense of Richmond.

He ordered Missouri-native Sterling Price to invade his home state and advance on St. Louis, capturing the city and its military arsenals.

Price was then told to cross into Kansas and turn south through the Indian Territory, "sweeping that country of its mules, horses, cattle, and military supplies".

However, the infantry units originally assigned to Price were ordered to the Western Theater, changing his mission from a full-fledged invasion into a cavalry raid.

Although Missouri pro-Union militia skirmished with the invading force almost daily, Price's first full battle did not come until September 27, at Pilot Knob, southwest of St. Louis in Iron County.

"[27] Nevertheless, Price's Missouri Expedition was a total failure and contributed, together with Union successes in Virginia and Georgia, to the re-election of President Lincoln.

This requires an inferior power to effectively use regular and irregular forces in concert (as was done by the North Vietnamese and Viet Cong against the French and Americans during the Vietnam War) to defeat a superior army.

Furthermore, he says, Price's insistence on guarding an ever-growing wagon train of looted military supplies and other items ultimately became "an albatross to [his] withdrawal.

"[29] Price, wrote Davis, ought to have used Confederate bushwhackers to harass Federal formations, forcing his Union foe to send large numbers of troops out to pursue them over wide ranges of territory.