With his white duck suits and his white horse, Wirz was dubbed “Death on a Pale Horse.”  Many felt that the name was particularly apt in regard to his handling of the prison raider problem.  What began as isolated incidents of prisoners preying upon other prisoners became an epidemic when these marauders formed an alliance.  Led by Willie “Mosby” Collins of the 144th New York, these thugs became known as “Mosby’s Raiders,” and at their peak they were 700 strong, armed with clubs, slingshots, brass knuckles and homemade knives.  Many of them bunked together in a large communal tent in one section of the stockade, a patchwork affair sewn together from rags and garments stolen from other prisoners. 

Some prisoners carried large sums of money with them, and they were prime targets for Mosby’s men.  The raiders employed “bunk steerers,” prisoners who befriended new arrivals to the stockade and directed them to the “best” available spots in the compound.  The steerers then informed the ruffians of the newcomers’ locations. 

Prisoners who fought back were subject to severe gang beatings.  Several prisoners were killed defending their belongings.  In one case a man murdered his own brother for the money sewn into his pants, then buried the corpse under his own bunking ground, sleeping every night on top of his brother’s bones.  The raiders operated by night, communicating with one another by whistling.  Whenever innocent prisoners heard whistling in the dark, they lay awake, waiting for the sounds that followed—the smack of fists and clubs hitting flesh followed by gut-wrenching moans and cries.

The prisoners were ready to do something drastic to end the tyranny of the raiders, and a forthright new arrival named Dowd demanded to speak to the commandant after a pack of raiders beat him bloody.  A mob of angry prisoners backed him up.  They asked Captain Wirz if they could assemble a police force of their own—or “regulators,” as they would be called—to protect the prison population from the raiders.  Wirz agreed to their proposal and provided the regulators with clubs to enforce the peace inside the stockade.  After consultation with General Winder, Wirz further empowered them to punish those they found guilty as long as they abided by the rules of court martial and obtained permission before meting out sentences.  Wirz wanted a swift end to the raider problem, so to hurry things along, he suspended the prisoners’ rations until all the raiders were captured.

On June 29, 1864, the regulators went to work, rounding up the worst of the raiders and dragging them to the gates where Confederate guards took custody of them, securing them in stocks or with ball and chain.  Nearly 200 raiders were captured, but Wirz felt that this was too many and ordered all but the most serious offenders back into the stockade.  Angry prisoners armed with clubs ran to the gates and formed a gauntlet for the released raiders.  Guards were ordered to fire buckshot at any raider who refused to run the gauntlet.  The raiders tried to break through the sides of the gauntlet, but even those who succeeded were pursued and bludgeoned.

General Winder granted the prisoners’ request to conduct their own trial for the worst of the raiders.  To get as impartial a jury as possible, 18 new prisoners fresh off the train were selected.  Three judges were elected, and several of the lawyers in the prison population volunteered to prosecute the cases.  “Mosby” Collins had enough money stashed away to hire a defense attorney from among the prison legal pool. 

A courtroom was set up in a shed outside the stockade gates.  Regulators ransacked the raiders’ tents, searching for evidence—cash, watches and other personal belongings stolen by the raiders.   The trial took place over a period of several weeks and adhered to the rules of military law.  Most of the accused were  found guilty of minor crimes, but Wirz would not let them serve out their sentences in separate quarters.  He ordered these men released back into the stockade.  Word of Wirz’s order spread fast, and when the gates opened to let these prisoners back in, a new gauntlet, now stretching 150 yards, was waiting for them. 

Six of the raiders, including “Mosby” Collins, were sentenced to death.  On General Winder’s insistence, the transcripts of the trial were sent to Washington for federal approval.  A letter allegedly signed by Abraham Lincoln granted the Andersonville prison court authority to execute the guilty.  On the morning of July 11, a crew of prisoners built a crude scaffold where the six men would be hanged.  It was devised so that all six would stand on a plank that would give way when the end props were pulled out, sending them to their doom simultaneously.     

Shortly after noon, Wirz on his pale horse escorted the condemned men into the stockades.  John McElroy in his 1899 memoir Andersonville: A Story of Rebel Prison, reported that Wirz in his thick German accent announced to the prison population, “Brizners, I return to you dese men so goot as I got dem.  You haf tried dem yourselves, and found dem guilty.  I haf had notting to do wit it.  I vash my hands of eferyting connected wit dem.  Do wit dem as you like, and may Gott haf mercy on you and on dem.  Garts, about face! Vorwarts, march!”

As the condemned were led to the scaffold, one man broke free and ran for his life.  Regulators chased him down and brought him back.  The other raiders in the camp and their sympathizers shouted and jeered, threatening to cause a riot to free their comrades.  The six men were given an opportunity to say their last words before they were hustled up onto the plank and nooses were fitted over their heads.  Two executioners pulled the ropes that released the props holding the plank.  The six men dropped, but Mosby’s frayed noose snapped.  The crowd surged, some calling for Mosby’s release in the face of a sign from God that he was innocent.  But the executioners quickly gathered him up, retied his noose, and pushed him off the scaffold.  The condemned raiders were left to twist in the wind for 27 minutes.

Captain Wirz’s cold, Pilate-like indifference regarding the condemned raiders seems to prove that the man had a heart of stone, but other accounts portray him as a gentleman of considerable kindness and charm.  The officers’ wives and the local Georgia ladies generally found him to be quite pleasant.  On one occasion he paroled several dozen Union drummer boys and put them to work outside the stockade to save them from the horrors of the stockade.  He even invited one of these boys to live in his own home.  

Wirz showed mercy on the Hunts and provided Mrs. Hunt and her baby with a private tent outside the stockade walls.  He paroled Captain Hunt and made him ward master of the hospital, so that he could be near his wife and son.