What is the “blue flu,” and why might it strike New York City police?

This weekend, officers from the New York City Police Department are rumored to be planning a walkout to protest calls to defund the police.

This builds on a similar tactic used by police in Atlanta less than a month ago. On June 16, Fulton County District Attorney, Paul L. Howard Jr. announced that Garrett Rolfe, the Atlanta police officer who fatally shot Rayshard Brooks, would face charges of felony murder and aggravated assault. That night, scores of Atlanta Police Department officers caught the “blue flu,” calling out sick en masse to protest the charges against Rolfe.

Such walkouts constitute, in effect, illegal strikes — laws in all 50 states prohibit police strikes. Yet, there is nothing new about the blue flu. It is a strategy long employed by police unions and rank-and-file officers during contract negotiations, disputes over reforms and, like in Atlanta, in response to disciplinary action against individual officers. The intent is to dramatize police disputes with municipal government and rally the citizenry to their side.

But the result of such protests matter deeply as we consider police reform today. Historically, blue flu strikes have helped expand police power, ultimately limiting the ability of city governments to reform, constrain or conduct oversight over the police. They allow the police to leverage public fear of crime to extract concessions from municipalities.

This became clear in Detroit more than 50 years ago. In June 1967, tensions arose between Detroit Mayor Jerome Cavanagh and the Detroit Police Officers Association (DPOA), which represented the city’s 3,300 patrol officers. The two were at odds primarily over police demands for a pay increase. Cavanagh showed no signs of caving to the DPOA’s demands and had, in fact, proposed to cut the police department’s budget.

On June 15, the DPOA escalated the dispute with a walkout: 323 officers called in sick. The number grew over the next several days as the blue flu spread, reaching a height of 800 absences on June 17. In tandem with the walkout, the DPOA launched a fearmongering media campaign to win over the public. They took out ads in local newspapers warning Detroit residents, “How does it feel to be held up? Stick around and find out!”

This campaign took place at a time of rising urban crime rates and uprisings, and only a month before the 1967 Detroit riot, making it especially potent. The DPOA understood this climate and used it to its advantage. With locals already afraid of crime and displeased at Cavanagh’s failure to rein it in, they would be more likely to demand the return of the police than to demand retribution against officers for an illegal strike.

The DPOA’s strategy paid off. The walkout left Detroit Police Commissioner Ray Girardin feeling “practically helpless.” “I couldn’t force them to work,” he later told The Washington Post. Rather than risk public ire by allowing the blue flu to continue, Cavanagh relented. Ultimately, the DPOA got the raises it sought, making Detroit officers the highest paid in the nation.

This was far from the end of the fight between Cavanagh and the DPOA. In the ensuing months and years, they continued to tussle over wages, pensions, the budget, the integration of squad cars and the hiring of black officers. The threat of another blue flu loomed over all these disputes, helping the union to win many of them.

And Detroit was not an outlier.

Throughout the 1960s, ’70s and ’80s, the blue flu was a ubiquitous and highly effective tactic in Baltimore, Memphis, New Orleans, Chicago, Newark, New York and many other cities. In most cases, as author Kristian Williams writes, “When faced with a walkout or slowdown, the authorities usually decided that the pragmatic need to get the cops back to work trumped the city government’s long term interest in diminishing the rank and file’s power.”

But each time a city relented to this pressure, they ceded more and more power to police unions, which would turn to the strategy repeatedly to defend officers’ interests — particularly when it came to efforts to address systemic racism in police policies and practices.

In 1970, black residents of Pittsburgh’s North Side neighborhood raised an outcry over the “hostile sadistic treatment” they experienced at the hands of white police officers. They lobbied Mayor Peter F. Flaherty to assign more black officers to their neighborhood. The mayor agreed, transferring several white officers out of the North Side and replacing them with black officers.

While residents cheered this decision, white officers and the Fraternal Order of Police (FOP), which represented them, were furious. They slammed the transfer as “discrimination” against whites. About 425 of the Pittsburgh Police Department’s 1,600 police officers called out sick in protest.

Notably, black police officers broke with their white colleagues and refused to join the walkout. They praised the transfer as a “long overdue action” and viewed the walkout as a betrayal of officers’ oath to protect the public.

Nonetheless, the tactic paid off. After several days, Flaherty caved to the “open revolt” of white officers, agreeing to halt the transfers and instead submit the dispute to binding arbitration between the city and the police union. Black officers, though, continued to speak out against their union’s support of racist practices, and many of them later resigned from the union in protest.

Similar scenarios played out in Detroit, Chicago and other cities in the 1960s and ’70s, as white officers continually staged walkouts to preserve the segregated status quo in their departments.

These blue flu strikes amounted to an authoritarian power grab by police officers bent on avoiding oversight, rejecting reforms and shoring up their own authority. In the aftermath of the 1967 Detroit walkout, a police commissioner’s aide strongly criticized the police union’s strong-arm tactics, saying “it smacks of a police state.” The clash left one newspaper editor wondering, “Who’s the Boss of the Detroit Police?”

But in the “law and order” climate of the late 1960s, such criticism did not resonate enough to stir a groundswell of public opinion against the blue flu. And police unions dismissed critics by arguing that officers had “no alternative” but to engage in walkouts to get city officials to make concessions.

Crucially, the very effectiveness of the blue flu may be premised on a myth. While police unions use public fear of crime skyrocketing without police on duty, in many cases, the absence of police did not lead to a rise in crime. In New York City in 1971, for example, 20,000 officers called out sick for five days over a pay dispute without any apparent increase in crime. The most striking aspect of the walkout, as one observer noted, “might be just how unimportant it seemed.”

Today, municipalities are under immense pressure from activists who have taken to the streets to protest the police killings of black men and women. Some have already responded by enacting new policies and cutting police budgets. As it continues, more blue flus are likely to follow as officers seek to wrest back control of the public debate on policing and reassert their independence.

But, with public opinion on the side of reform, the blue flu may prove to be a less effective strategy than in the past. In fact, if the myth of the blue flu proves true and less policing does not result in more crime, such tactics may actually give a boost to the very argument about defunding the police and reining in their power that officers are protesting.