The outcry against police militarization is finally producing echoes in the halls of congress, and long-overdue restrictions on the Department of Homeland Security’s 1033 program seem inevitable. However, this practical step only scratches the surface. Few have dared ask the much more uncomfortable question: why have a shockingly high number of American police departments felt entitled to stockpile and even unleash weapons of war upon their own communities?

The answer is staring us directly in the face. Even as President Obama continues to expand American military operations in the Middle East to confront ISIL, almost no one is talking about the intrinsic connection between police militarization and America’s ironic moniker of "policeman of the world." It was easy to chuckle when comedian John Oliver noted that Keene, New Hampshire ordered an armored personnel carrier to thwart terrorism at their annual pumpkin festival. However, police departments in even the most remote enclaves of rural America have accepted and even delighted in the prospect of being auxiliaries on the domestic front of the global war on terrorism – an attitude which is reinforced with each and every bomb dropped in the Middle East.

Now more than a decade later, President Bush’s promise that "we fight them there, so we don’t have to fight them here" has blossomed into a spectacular irony: imperialism abroad is inspiring imperialism at home.

Suggesting that average police officers have become connected, even accidentally, to a larger imperial project may seem outlandish to some, yet a deeper understanding of the historical, cultural and linguistic roots of "imperialism" itself clarifies what has happened to America’s police. The English word "imperialism" is derived from the ancient Latin term imperium, an over two-thousand-year-old Roman concept which signified the power of an official to command and to expect automatic compliance. The key to imperium is in its assignment of hierarchy: it not only describes the authority of an official, but it requires resigned passivity by those whom the official encounters.

Although "police imperialism" may seem difficult to comprehend, examples of police imperium are seen on a daily basis. Police exercise imperium by reacting excessively when average citizens politely invoke their civil rights or ask clarifying questions. Just a few days ago, Santiago Hernandez was frisked by New York police and dared to ask them why. He was subsequently handcuffed, thrown to the ground, pummeled with night sticks, pepper sprayed and beat ‘like it was a gang’ doing it. Hernandez did not break any laws, but he challenged the prevailing imperium of the officers.

What happened to Hernandez was not an isolated incident; the issue is systemic. If police are given the weapons, ethos and imperium of soldiers, should we be surprised if they act like soldiers? Martial law on the streets of Ferguson, the violent suppression of the Occupy protests, babies burned in their cribs during no-knock SWAT raids to serve search warrants – Americans are used to such things occurring in far-flung foreign lands. Again, we might point to the weapons and equipment being used in such activities, but such things only enable police aggression, they do not cause it.

The parallels between police overreach and imperium go much farther. In order to effectively promote the interests and glory of the state, Roman magistrates and officers with imperium were shielded from many of the normal social and cultural checks on such power. So too have American courts routinely upheld the rights of police to use artifice and deception to obtain convictions and create evidence for arrests. Asset forfeiture laws protect the prerogative of police to confiscate and keep property of the accused, even before any criminal conviction has been obtained. Imperium similarly enabled Roman officials to lie, coerce and exploit residents of imperial provinces even while their nominal remit was to promote justice and ensure safety.

The similarities extend into accountability mechanisms as well. When Roman magistrates were accused of abusing their imperium, they were tried by an internal court composed of members of their own class. The incentives for elites to protect fellow elites and to ensure that the power of imperium would be preserved for them when it was their turn resulted in few convictions and punishments. The main institutional mechanism for protecting citizens from rouge police officers are Internal Affairs units – these internal branches of police departments, however, are usually staffed by former and even current police officers. Unsurprisingly, these units – which often lack any democratic or citizen oversight – can and have acted as a circle of wagons rather than an impartial arbiter between citizens and their police.

The imperium granted to police, and the hierarchy it creates, has produced an unfortunate, yet foreseeable result: police officers which act like an army of occupation, and communities that have become territories to be occupied. Perhaps this is why the events in Ferguson are so unsettling; because the empire which Americans have long dared not question has finally come home.

Colin P. Elliott is a Postdoctoral Fellow in Classics and Ancient History at Washington and Lee University where he writes and teaches on ancient imperialism, the Roman economy, and the collapse of the Roman Empire