The New York Times reports: Riot police officers tear-gassing protesters at the Occupy movement in Oakland. The surprising nighttime invasion of Zuccotti Park in Lower Manhattan, carried out with D-Day-like secrecy by officers deploying klieg lights and a military-style sound machine. And campus police officers in helmets and face shields dousing demonstrators at the University of California, Davis with pepper spray.

Is this the militarization of the American police?

Police forces undeniably share a soldier’s ethos, no matter the size of the city, town or jurisdiction: officers carry deadly weapons and wear uniforms with patches denoting rank. They salute one another and pay homage to a “Yes, sir,” “No, sir,” hierarchical culture.

But beyond such symbolic and formal similarities, American law and tradition have tried to draw a clear line between police and military forces. To cast the roles of the two too closely, those in and out of law enforcement say, is to mistake the mission of each. Soldiers, after all, go to war to destroy, and kill the enemy. The police, who are supposed to maintain the peace, “are the citizens, and the citizens are the police,” according to Chief Walter A. McNeil of Quincy, Fla., the president of the International Association of Chiefs of Police, citing the words of Sir Robert Peel, the father of modern-day policing.

Yet lately images from Occupy protests streamed on the Internet — often in real time — show just how readily police officers can adopt military-style tactics and equipment, and come off more like soldiers as they face down citizens. Some say this adds up to the emergence of a new, more militaristic breed of civilian police officer. Others disagree.

What seems clear is that the terrorist attacks of Sept. 11, and the federal Homeland Security dollars that flowed to police forces in response to them, have further encouraged police forces to embrace paramilitary tactics like those that first emerged in the decades-long “war on drugs.”

Both wars — first on drugs, then terror — have lent police forces across the country justification to acquire the latest technology, equipment and tactical training for newly created specialized units.