Chicago came under martial law after the Great Fire. Did it help?

On Oct. 8, 1871, the Great Chicago Fire devastated the city. More than 17,500 buildings burned, 300 people died and up to one-quarter of the city’s residents were left homeless.

Three days later, the mayor of Chicago declared martial law. Hundreds of federal troops marched into the city to keep the peace, and a volunteer militia was established to patrol the neighborhoods.

This military occupation ended less than two weeks later, after one elected official confronted another and after a military cadet fatally shot a civilian.

While reading about this moment in history, a Curious City listener saw parallels to Operation Midway Blitz, President Donald Trump’s aggressive immigration enforcement campaign that began last fall, and asked us to take a closer look. Another Curious City listener had a related question about recent actions by U.S. Immigration and Customs Enforcement and Border Patrol: Was Chicago experiencing martial law? What is martial law, anyway?

To answer each of these questions, Curious City spoke with a historian, a handful of law professors and the author of a recent book about the aftermath of the Great Chicago Fire.

What is martial law?

Martial law is the temporary substitution of military authority for civilian rule in an emergency, but legal experts say the term is hard to define because it is not specifically described in the U.S. Constitution or in federal law.

“There’s a reason that martial law isn’t something that’s written down in the law books,” said Paul Gowder, a law professor at Northwestern University. “Because, in essence, martial law is an exception to the law.”

The Founding Fathers left martial law out of the Constitution because they did not want to write a guidebook outlining how a leader could put the military in charge, Gowder said: “They didn’t want it to be lawful for anyone to declare at all.”

What we’re left with instead are examples from history. During the Civil War, President Abraham Lincoln declared martial law in some areas of the South and suspended habeas corpus, the legal action that allows detainees to challenge the legality of their imprisonment in front of a judge. In the 1700s, the King of England sent soldiers from Great Britain to police the American colonies.

“That was one of the instigating reasons for the American Revolution,” said Alison LaCroix, a constitutional law professor at the University of Chicago. “So this mixing of the military and the civil authorities is antithetical to our whole system of government.”

Today, martial law might be declared after an emergency that causes civilian authorities like your local police and court system to cease functioning. The military then steps into the gap upon the declaration of a mayor, a governor or a president.

“[The military is] in charge of policing. They are maybe defining what the law is,” LaCroix said. “They have pretty broad control, although they don’t get to suspend the Constitution.”

That’s partly why these legal scholars say Operation Midway Blitz is not an example of martial law. Civilian courts and civilian law enforcement are open and operating. Additionally, federal agents from Border Patrol, ICE, and the Department of Homeland Security are not part of the military chain of command, however militarized their attire, equipment or actions may be. Even when Trump sent the National Guard to Chicago against the wishes of local leaders, the Supreme Court stopped their deployment, saying the president failed to explain why the action was warranted.

Johns Hopkins University professor Tad Stoermer offers another take, arguing that recent actions by ICE and the Border Patrol, while perhaps not “legally” martial law, are “functionally” martial law.

“Being able to impose military authority over a civilian jurisdiction, that’s exactly what’s going on,” Stoermer said. “It just happens to be more surgical and targeted in the way the Trump regime is deploying it than we’ve seen done historically.”

Stoermer is the author of a forthcoming book, “A Resistance History of the United States.” He said that our question may be better posed to the people who are being detained by Border Patrol and ICE agents.

“They are, in fact, not having access to the same kind of rights and protections. And even habeas corpus is being suspended for them,” Stoermer said. “They will get put on a plane and sent to Louisiana overnight. That is hardly the civilian courts working as designed.”

Gowder said not calling this martial law isn’t a defense of it. He called the actions of immigration agents “abusive,” but in a way that still operates within the civilian legal system.

“I think we’re seeing routine violations of the Fourth Amendment, in terms of illegally searching people [and] in terms of illegally breaking into homes without a warrant. I think we’re seeing a ton of violations of the due process clause of the Fifth Amendment in terms of subjecting people to deportation without adequate hearings,” Gowder said. “None of this is okay. All I’m saying is that it doesn’t constitute martial law as we ordinarily use the term.”

The Department of Homeland Security has repeatedly denied it arrests people in violation of the Fourth Amendment.

Ultimately, the question of who has the authority to trigger martial law is just as important as what it looks like, according to LaCroix. In constitutional law, it’s the “who decides” question.

“What is the situation on the ground and who decides when the emergency is triggered?” LaCroix said. “And if all the power is in the hands of the president, […] that is what the founders thought was a recipe for tyranny and despotism.”

The Founding Fathers designed a system of federalism because they wanted state governments, local governments and the central government to all check each other, LaCroix said.

“This notion that no one should stand in the way and the president could just do whatever he wants is antithetical to everything in the Constitution,” she said.

The question of “who decides” eventually came to a head in Chicago in the days after the mayor declared martial law in 1871.

Martial law after the Great Chicago Fire

Post-fire Chicago was a place of rumor and unreliable information, according to Scott W. Berg, professor at George Mason University and author of the 2023 book “The Burning of the World: The Great Chicago Fire and the War for a City’s Soul.” Amid stories of crime and chaos, the city’s business elite went to Chicago Mayor Roswell B. Mason and insisted he protect their remaining financial interests.

The mayor issued a proclamation on Oct. 11, 1871, that Berg called “100% de facto martial law.” It entrusted “the preservation of the good order and peace of the city” to Lt. Gen. Philip Sheridan, a Civil War hero and local celebrity. Sheridan marched in a few hundred federal troops, but what he saw on the ground was far from the mayhem reported by the newspapers.

“There has been no case of violence since the disaster of Sunday night and Monday morning,” Sheridan wrote to Mason on Oct. 17. “There has not been a single case of arson, hanging, or shooting — not even a case of riot or street fight. I have seen no reason for the circulation of such reports.”

Despite the lack of chaos, Sheridan also created volunteer “city militias” composed mostly of local students and the unemployed.

“Their job was essentially just to patrol their own neighborhoods,” Berg said. “They hand them a bunch of guns and they say, ‘Okay, here’s the structures. Learn it really quickly. You’re on duty tonight, OK?’ And that leads to problems.”

Late on the night of Oct. 20, a city attorney named Thomas Grosvenor was walking home through the Old University of Chicago campus when he encountered a 20-year old sophomore named Theodore Treat, who was armed and on patrol as one of Sheridan’s “University Cadets.” Treat twice commanded Grosvenor to halt. After Grosvenor refused and told Treat to “go to hell,” Treat shot him. Grosvenor died several hours later.

“This is a disaster for the militias and the federal control of the city, because the papers now have something other than supposed chaos to report on,” Berg said. “They have the actual shooting of a city attorney by this young kid who had been handed a rifle.”

Public support for the military occupation quickly evaporated. Newspapers that initially supported the move came out against it.

Happening at nearly the same time, a private confrontation was taking place between the mayor and the governor. Illinois Gov. John Palmer sent Chicago Mayor Mason a strongly worded letter just a few hours before the shooting. It expressed Palmer’s “profoundest mortification” at the mayor’s decision “to have practically abdicated your functions as mayor” by opting for “the employment of military force for the protection of the city.” Palmer also believed the presence of troops unanswerable to civil authorities was illegal and asked Mason to relieve Sheridan of his duties.

Within 48 hours, the volunteer militia was disbanded, the federal soldiers were boarding trains back to Kansas, Kentucky and Nebraska, and Sheridan’s time as military leader was finished “as quickly and as shrouded in secrecy as it had begun,” Berg writes.

That said, the events of 1871 are not comparable with Operation Midway Blitz in Chicago or Operation Metro Surge in Minneapolis. Agents with Border Patrol and ICE do not fall under the chain of military command, and local leaders in Illinois and Minnesota are mostly aligned in their beliefs that military tactics are not necessary for immigration enforcement.

But Berg said one parallel does strike him: people with guns hastily trained.

“I'm very, very struck by the creation of sort of a quasi-paramilitary force,” he said. “I see the unpreparedness of some of the people doing this as a key comparison.”

Last month, CNN reported that new ICE agents are receiving less training than almost any other federal agents. DHS pushed back on that analysis, saying new ICE recruits receive 56 days of training and that no training requirements have been removed.

Berg said another parallel is the swift public reaction to the death of a citizen at the hands of federal forces.

“In today’s discussions, especially in light of Minneapolis, [...] a very large portion now of the American public is sort of like, ‘Well, we understand the aims, but you’re just doing it all wrong,’” Berg said. “And in Chicago in 1871 — which is a sort of microcosm and a precursor to all this, in some ways — you’re seeing people just say, ‘Well, if this is what it’s gonna be, forget it.’”

As a final comparison, Berg said that in 1871, there was “a strong sense among the public that the folks doing this had learned their lesson by the death of Grosvenor,” the city attorney shot by an armed cadet.

After immigration agents fatally shot Silverio Villegas-Gonzalez, Ruben Ray Martinez, Renee Good and Alexi Pretti, Trump told NBC that he learned “maybe we could use a little bit of a softer touch,” but that immigration enforcement should still be “tough.” It remains to be seen what changes, if any, the administration will make to its immigration enforcement operations going forward.

Justin Bull is a producer for Curious City.