As a native of the Baltimore area, I watched the recent scenes of urban destruction with intense interest and profound sadness. There are so many things to say about an event like this, and everyone has been rushing to say them. I will confine myself, for now, to a brief comment on Riot Prevention 101.

Back in 2008, Michael Barone published a fascinating article on the 1967 Detroit riots, which he witnessed up close as an intern in the office of Mayor Jerome Cavanagh. The carnage in Detroit left 43 people dead, and it prompted countless writers and scholars to search for the “root causes” of the violence. Yet far too many analysts overlooked perhaps the most basic lesson of all riots. As Barone put it: “Riots occur when people expect a riot to occur and think they can get away without punishment.”

Thus, the key to preventing an angry mob from becoming a rioting mob is to respond swiftly and effectively to the first outbreak of lawless behavior. Baltimore mayor Stephanie Rawlings-Blake failed to do that, and her city suffered the consequences.

Needless to say, we’ve seen this happen over and over again in cities across America. Writes pseudonymous Los Angeles police officer Jack Dunphy:

It’s all so familiar, isn’t it? Some outrage occurs, real or imagined, soon to be followed by “peaceful protests,” the peacefulness of which devolves into violence.

Such was the case in Miami in 1989, Crown Heights in 1991, Los Angeles in 1992, Oakland in 2009, and just last year in Ferguson, Mo. In these cases and in others too numerous to list, the historical antecedents were ignored in the name of allowing the protesters to “vent their rage.” The results are always the same: theft and destruction of property, injuries, and sometimes even the loss of life.

Anyone who failed to anticipate what is now occurring in the streets of Baltimore is unfit to hold public office or to lead the police officers who bear the task of restoring order in the city, a task made all the more difficult by the manifest failures of Baltimore mayor Stephanie Rawlings-Blake. . . .

How frustrating it is to watch on television as hundreds of uniformed police officers stand by while thugs throw rocks, bottles, and bricks at them, and as businesses are looted and burned nearby. For this I do not blame the rank-and-file cops, more than a dozen of whom have been injured at the time of this writing. Instead I blame their leaders who have failed to heed a lesson of the not-too-distant past: If you allow lawlessness to go unchallenged, you will very quickly have more of it.

The late journalist Eugene Methvin, an expert on riots, made this same point nearly a quarter-century ago: “The lesson of history is plain: In riot situations, the earlier the police make arrests, and the more arrests they make, the lower will be the toll in life, limb, and property. And the cop on the street will not act decisively unless he feels he has the support of his superiors — principally his chief and mayor.”

We’ll never know for certain whether a more forceful response would have stopped the disorder in Baltimore from exploding into a full-blown riot. Yet history does indeed suggest that a stronger initial response would have reduced the violence significantly. It is depressing that so simple and obvious a lesson should have to be relearned so many times, and at such high cost.