In many ways, the history of America’s Global War on Terror, now entering its 17th year, is also the history of drone warfare. From its early use as ambitious battlefield surveillance, drone technology was quickly expanded to specialized assassination, and finally to general warfare in places like Afghanistan, Iraq, Syria, Somalia, and Yemen. By 2014, the U.S. Air Force wastraining more remote drone pilots than pilots for all of its warplanes combined.

Drones were once an exclusive technology of the United States, but it did not stay that way for long. America’s military is, after all, the world’s largest, and a shift in its priorities toward drone warfare did not go unnoticed by the rest of the world. This has meant the rise of cheaper combat drone manufacturers in China, opening the technology up to arsenals around the world. Even cheaper civilian technology has also emerged, giving terrorist organizations access to their own makeshift fleets.

This is where it gets scary. Not surprising, mind you, but disturbing nonetheless.

Tech-savvy ISIS is now at the forefront of developing improvised military drones. Starting as America did with simple surveillance and modifying civilian camera drones using off-the-shelf components, ISIS quickly followed the American path ofmilitarizing the drones.

Much like the improvised explosive devices (IEDs) that confounded our conventional forces on the battlefield, killing and wounding thousands of American soldiers over the last decade in Iraq and Afghanistan, the dramatically less resourced, “ragtag” insurgency is again using our own weapons against us.

It’s not that ISIS has a “drone program” as such. Rather, drones have become so ubiquitous, in no small part because of the American military’s substantial investment, that off-the-shelf options are everywhere, and little know-how is needed to modify retail drone solutions to drop explosives on enemy forces. The drones are so cheap that ISIS has at times decided even this isn’t necessary, and simply straps the explosives to drones and uses them as unmanned “suicide” bombers.

Many warned about America’s use of drones as a largely extra-judicial means of assassination. It was a dangerous precedent, and one that would inform nations and organizations around the world as they too embraced the killer technology. We all knew that someday the “bad guys” would get it too, maybe just not this soon.

Nations are now joining “the drone club” by the dozens, and militant groups are not far behind. Nations like Nigeria have embraced drones for killing on the cheap, and without the pesky oversight that comes from having an identifiable pilot. ISIS has been a proof of concept for unconventional drone warfare at what appears to be little cost. This has the Pentagon scrambling to develop anti-drone technology, and adding it to the world’s largest drone fleet.

But drone technology marches on at a rapid pace. Costly anti-drone weapons may appear on the battlefield and work for a time, but will likely function as air defense technology did, on a more rapid time frame: an endless cycle of improvements to circumvent defenses, and new defenses to take their place.

But the one advance that can be reliably counted upon, above all others, is cost reduction. That’s not a strong suit for the Pentagon, but commercial drones are already, at the lowest end, children’s toys. As they get ever-cheaper and ever more advanced, groups like ISIS will have makeshift air forces—and not just on the traditional battlefield.

And that is perhaps the scariest future of all. America’s drone wars have a generation of people in Pakistan and Yemen accustomed to foreign attack drones looming over cities and towns, attacking with impunity. As such drones become more widespread, this will be true of cities in more countries. Eventually, groups like ISIS will have the capacity to field a drone fleet over Western cities in Europe and America.

This is blowback of the worst kind. The ill-considered decision by U.S. officials to rush headlong into the casual use of drones as killing tools has accelerated the now nascent global drone war. With endless targets across the world and so many different drone fleets, it will be increasingly difficult to discern exactly whose drones are operating in any given place.

Having opened the Pandora’s Box of drone warfare, it is unclear what we can do about it. For groups like ISIS, this is a new, permanent tool in its kit, and little can be done about that. Nation-states, on the other hand, could be reined in somewhat by a more clear international legal standard for lethal drone use.

The primary problem with achieving this is that the entire U.S. history of drone warfare has been one of opacity and unaccountability. The Pentagon has been a bit more transparent about individual strikes than the CIA, but both have underreported civilian deaths that helps skirt any sense of real responsibility.

Revisiting the CIA era of the drone war, making it clear in no uncertain terms that crimes were committed, and holding those involved to account would go a long way towards retroactively setting a legal standard for killing people with unmanned aircraft.

America must right the wrongs it committed before those wrongs become standard operating procedure for the world of drones we now find ourselves stuck in. If it’s not too late already.

Jason Ditz is news editor atAntiwar.com, a nonprofit organization dedicated to the cause of non-interventionism. His work has appeared in Forbes, Toronto Star, Minneapolis Star-Tribune, Providence Journal, Daily Caller, the American Conservative, Washington Times and Detroit Free Press.