In 1864, Union General Steele’s failure in the Camden Expedition (March 23–May 2, 1864,) can in no small part be laid to Shelby’s brilliant and determined harassment, though in concert with other Confederate forces. Ultimately that Federal force was forced back to Little Rock upon the final destruction or capture of its supply trains at Mark’s Mill. Reassigned to the Clarendon, Arkansas area, Shelby accomplished the rare feat of capturing a Union tinclad USS Queen City, which was immediately destroyed to avoid recapture. As summer was ending Shelby then commanded a division during Sterling Price’s Missouri raid. He distinguished himself at the battles of Little Blue River and Westport, and captured many Union held towns, including Potosi, Boonville, Waverly, Stockton, Lexington, and California, Missouri.
Shelby’s adjutant was John Newman Edwards, who later as editor of the Kansas City Times was to almost single handedly create the anti-hero legend of Jesse James.
After Robert E. Lee’s army surrendered in Virginia, General Edmund Kirby Smith appointed Shelby a major general on May 10, 1865. However, the promotion was never formally submitted, due to the collapse of the Confederate government.
In June 1865, rather than surrender, Shelby and approximately 1,000 of his remaining troops rode south into Mexico. For their determination not to surrender, they were immortalized as “the undefeated”. A later verse appended to the angry post-war Confederate anthem, “The Unreconstructed Rebel” commemorates the defiance of Shelby and his men:
“I won’t be reconstructed, I’m better now than then.
And for a Carpetbagger I do not give a damn.
So it’s forward to the frontier, soon as I can go.
I’ll fix me up a weapon and start for Mexico.”
Their plan was to offer their services to Emperor Maximilian as a ‘foreign legion.’ Maximilian declined to accept the ex-Confederates into his armed forces, but he did grant them land for an American colony in Mexico near Vera Cruz. The grant would be revoked two years later following the collapse of the empire and Maximilan’s execution. Reportedly, Shelby sank his battle flag in the Rio Grande near present-day Eagle Pass (TX) on the way to Mexico rather than risk the flag falling into the hands of the Federals. The event is depicted in a painting displayed at the Eagle Pass City Hall. The memory of Shelby and his men as “The Undefeated” is used as a distant basis for the 1969 John Wayne-Rock Hudson film by the same name.
Shelby returned to Missouri in 1867 and resumed farming. He was appointed the U.S. Marshal for the Western District of Missouri in 1893, was a critical witness for the defense of Frank James at his trial, and retained the position until his death in 1897. He died in Adrian, Missouri, and is buried in Forest Hill Cemetery, Kansas City.