Iranian Supreme Leader Ayatollah Ali Khamenei, seated left, listens to an official during his visit to an aerospace exhibition in Tehran, Iran, on Sunday, May 11. The exhibition revealed an advanced CIA spy drone, at front, captured in 2011 by Iran, and its Iranian-made copy, at back. 
Iran says it built its drone by reverse-engineering the U.S. drone. 
Iran says its new drone is a copy of Lockheed Martin's RQ-170 Sentinel. 
Iran says it was able to commandeer the U.S. drone, rather than shooting it down.
- Peter Bergen says use of drones for military purposes is going to proliferate
- Drones enable warfare to be fought at lower cost without risking pilots' lives
- They offer more precise targeting but still will kill civilians and thus will stir debate
- Bergen: Ethical and legal questions raised by the use of armed drones abound
Editor's note: Peter Bergen is CNN's national security analyst, a director at the New America Foundation and the author of "Manhunt: The Ten-Year Search for bin Laden -- From 9/11 to Abbottabad."
(CNN) -- Drones are everywhere.
Consider that just in the past few days, a Federal Aviation Administration official revealed that in March a US Airways passenger jet nearly collided with a small-unmanned aircraft that looked similar to an F-4 Phantom jet and was flying above 2,000 feet over Florida. These details and the fact that the drone was described as "camouflaged" suggest that it was not a civilian drone.
Then Sunday the Iranians announced that they had engineered a copy of a highly sophisticated U.S. surveillance drone that they had captured in 2011. Iran's state television showed footage of what they claimed was a replica of the American RQ-170 Sentinel drone. A photograph showed Iran's Supreme Leader, Ayatollah Ali Khamenei, sitting next to the drone.
The same day that the Iranians showed off their new drone, Sen. Rand Paul, R-Kentucky, wrote an op-ed in The New York Times arguing against the appointment of David Barron as a federal judge. Barron was a White House lawyer who was involved in drafting the legal opinions used to justify the 2011 drone strike in Yemen that killed Anwar al-Awlaki, an American citizen who had taken a leadership role in al Qaeda.
Paul wrote, "Killing an American citizen without a trial is an extraordinary concept and deserves serious debate. I can't imagine appointing someone to the federal bench, one level below the Supreme Court, without fully understanding that person's views concerning the extrajudicial killing of American citizens. ... I believe that all senators should have access to all of these opinions. Furthermore, the American people deserve to see redacted versions of these memos so that they can understand the Obama administration's legal justification for this extraordinary exercise of executive power."
Not so long ago, killing an American citizen on the other side of the world with an armed drone would have been in the realm of science fiction. Before 9/11, the United States had only a handful of experimental drones that had never been used to kill anyone. Today, there are at least 7,000 drones in the U.S. arsenal, more than 200 of which are armed drones and that have killed thousands of people.
This large American fleet of drones is a harbinger of an important trend. Armed drones will likely prove as important to the future of warfare as tanks were during World War II. We can expect to see them used not only by the United States, but also by other countries such as China and Russia that are jumping into the production of armed drones.
Impact of U.S. drones in Yemen 
Airliner's near miss with drone 
A U.S. Air Force MQ-1 Predator UAV assigned to the California Air National Guard's 163rd Reconnaissance Wing flies near the Southern California Logistics Airport in Victorville, California, on January 7, 2012. 
A model of of the European "Neuron" UAV at the Paris Air Show in Le Bourget, France in 2005. The UAV is an European Research project led by Dassault Aviation. 
An MQ-9 Reaper unmanned aircraft vehicle (UAV) sits in a shelter at Joint Base Balad, Iraq, after a mission on November 10, 2008. According to the U.S. Department of Defense, the Reaper can carry up to 3,750 pounds of laser-guided bombs and missiles. 
A British MQ-9 Reaper sits on a runway on March 17. Both British and American Reapers are deployed to Afghanistan. 
U.S. Marines perform operational checks on a Marine Squadron Two (VMU-2) UAV before a launch at Speed Bag Airfield, near Niland, California, on October 25, 2011. 
An Iranian-made drone is displayed during the Army Day celebrations in Tehran on April 18, 2010. 
A model of a surveillance drone built by Dassault Aviation and BAE Systems is displayed at the International Paris Air show in 2011. 
An Israeli Hermes 500 UAV flies over the Hatzerim air force base near Beersheva, Israel, during an air show at the graduation ceremony of Israeli pilots on June 30, 2011. 
Chinese visitors examine an unmanned helicopter drone at the China Aviation Expo in Beijing on September 21, 2011. 
Israeli soldiers prepare to launch a Skylark drone during a drill on January 16, 2012 near Bat Shlomo, Israel. The Skylark can carry a camera payload of up to 1 kilogram, has an operational ceiling of 15,000 feet, and allows users to monitor any designated point within a 15-kilometer radius. The Skylark unit consists of a ground control element and three drones, which provide battalion-level commanders with real-time information. 
An Israel Aerospace Industries UAV on display at the Singapore Airshow on February 15. 
A model of China's "Dark Sword" UAV. According to Jane's Defense & Security Intelligence & Analysis, the drone remains only a model, but offers an example of where China may go with its drone technology. Photos: Military drones 
Herding sheep, delivering pizza, guiding lost students around campus -- these are just a few things friendly drones can do. Company and DIY drones are on the rise, and not even Hollywood stars will be safe from them. Soon starlets might be acting in front of drone-mounted cameras or being chased by a UAV paparazzi. 
U.S. start-up Matternet aims to create a network of drones capable of transporting potentially lifesaving goods to rural and under-developed areas. The Bill & Melinda Gates Foundation is backing rural drone transport too, funding a project that aims to transport vaccines to hard-to-reach and disaster-struck locations. 
In Peru, archeologist are using drones to map archeological sites and protect them from vandals and squatters. 
Japanese toy maker Kyosho has developed an infrared controlled drone 'Neon Messenger', which can display LED messages while flying. 
Drones turn campus guide at -- where else -- MIT. Skycall is a prototype to help Harvard students navigate around MIT's infamously convoluted landscape. It was developed by an MIT research group called Senseable City Lab. 
Drone+stuffed cat = art. Orville is a flying helicopter cat made by Dutch artist Bert Jansen. The remote-controlled quadcopter was first exhibited in Amsterdam and Jansen has since created more taxidermy drones. German communications provider Deutsche Telekom is tired of people stealing their copper cables. So they contracted a company to tag overhead telephone cables with drones across Germany in an effort to fight theft of the cables, which has shot up in recent years with the value of copper. 
Pizza delivery company Domino's has tested the possibility of delivering pizza via the DomiCopter. Other companies are also investigating the possibility of delivering their food via drones. 
Drones, often more resilient than humans, make for an ideal search party, as they can be pre-programmed to scan an area inch-by-inch. Los Angeles County Sheriff's Department began experimenting with the SkySeer Search and Rescue drone as early as 2006. 
Soon, real farming could be as easy as online farming games. Time-consuming agricultural tasks, such as spraying pesticides, could be left to UAVs, whilst surveillance drones can analyze the land and offer insight into how to boost the harvest. This French drone is scanning crops to help farmers optimize water levels and fertilizer use. 
The Burning Man festival in Nevada is often a hotbed of amateur UAV activity. So much so that some look to the event for insight on how to balance freedom of drone use with privacy and safety concerns. 
Drones as shepherds? Quadcopters could soon be replacing dogs as herders. 
The French Fly-n-Sense company has developed an innovative forest surveillance system which will enable a real-time monitoring of fire outbreaks and the development of flames in French southwestern forests. 
Efforts to protect four of the world's last remaining northern white rhinos have been boosted by a $70,000 drone. The Ol Pejeta Conservacy in Kenya is planning to use the UAV to monitor the location of its wildlife and deter poachers from harming the animals. 
UAV technology company 3D Robotics has developed the X8, a copter that can take high-resolution videos and photographs, an do detailed mapping. 3D Robotics says the user will be able to create, fly and repeat missions for data measurement. Photos: 15 cool drones But armed drones raise a number of moral and political issues that are unresolved. In Pakistan, the CIA drone campaign is deeply unpopular because Pakistanis ask themselves: What gives the United States the right to invade the sovereign airspace of our nation and sometimes kill our civilians, even in the service of the laudable goal of killing al Qaeda militants?
For American readers, do a thought experiment in which armed Mexican drones were routinely killing members of drug cartels living in Texas, but they were also sometimes killing a number of ordinary Texans and you get a sense of how the average Pakistani thinks about this issue.
In Yemen, the U.S. drone campaign has also become increasingly controversial because drones continue to kill Yemeni civilians -- as they did last month in a strike that targeted members of al Qaeda's Yemeni affiliate. In that strike on April 19, at least nine militants were killed but so were three civilians.
Even with these issues, drones present features that make them appealing to political and military leaders. Drones are not simply pieces of artillery that happen to fly. They have four characteristics that mean they are likely to reshape warfare at a tactical level.
First, armed drones are different from any previous form of artillery because they can linger over and assess a target for many hours. That capability can quite dramatically lower the civilian casualty rates that have been typical of earlier eras of warfare.
The smallest bomb dropped by the U.S. Air Force is typically 500 pounds. Such a bomb cannot, of course, distinguish between a civilian and a combatant. A drone can do so. And it can also shoot much smaller missiles, such as the 100-pound Hellfire missile.
In that sense there is a case to be made that armed drones presage a more ethical form of warfare that kills fewer civilians. But that doesn't mean of course that drones and the people who operate them won't kill civilians in the future. The U.S. drone campaigns in Pakistan and Yemen have killed hundreds of civilians over the past half decade.
Second, armed drones also make it possible to wage war against particular individuals. In a sense drones are flying assassins that target particular people.
It is not an accident that the rise of drone warfare has coincided with America's unconventional war against al Qaeda and its allies. In conventional wars, armies wearing uniforms attack each other. But in the kind of drone warfare that the United States has conducted since 9/11 outside of conventional war zones in countries such as Pakistan and Yemen, drone strikes are not directed at someone because of his status as a uniformed member of another military force, but rather because of the individual's suspected connection to al Qaeda or an allied group.
Bergen: Target an American with drones?
Third, there is a lower threshold for the use of force when armed drones are an option. In many ways the use of armed drones is akin to the use of cyberwarfare. Both tactics greatly reduce or eliminate the number of deaths that would result from a conventional armed conflict. And whoever launches a drone attack or a cyberattack pays no costs of the kind that would typically take place on a conventional battlefield.
You can't shoot down a drone pilot or kill a computer technician launching some kind of cyberattack thousands of miles from the intended target. For this reason, drones and cyber capabilities can make conflict more likely as the barriers to engage in either drone warfare or cyberconflict are so low. (Until, of course, the opponent has the resources to retaliate in kind.)
Fourth, drone warfare is taking place in an unprecedented information environment in which the U.S. government collects ever-vaster amounts of data. This data collection is so extensive that the National Security Agency, for instance, can record every phone call that is made in a particular country.
It is this merger of "big data" and drone technology, which is also complemented by human intelligence about suspected terrorists provided by CIA assets on the ground in places such as Pakistan's tribal regions, that has made drone warfare against al Qaeda and its allies so effective.
The CIA drone campaign in Pakistan has killed 58 militant leaders, according to a count by the New America Foundation. Thirty-five militant leaders have also been killed in Yemen. Meanwhile, at least 339 civilians have been killed as well as at least 2,200 foot soldiers in militant groups in Pakistan and Yemen. At least 230 other people were reported killed, though it was not clear from reliable news accounts if they were militants or civilians.
Indeed, using the most conservative estimates from a database of drone attacks maintained by the New America Foundation, the Obama administration authorized the killing of more than 2,400 people in drone strikes in Pakistan and Yemen from the time it first assumed office until the end of March 2014. (Using the least conservative estimates from that database, the total number of people killed was almost 4,000.)
Put another way, using the most conservative estimates of the numbers of people killed in drone strikes by the Obama administration, they amount to three times the total number of the some 800 prisoners at the Guantanamo prison camp placed there by the Bush administration. As President Barack Obama reportedly told some of his aides, "Turns out I'm really good at killing people. Didn't know that was going to be a strong suit of mine."
Osama bin Laden recognized the devastation that such drone strikes were inflicting on his organization, writing a lengthy memo about the issue that was later recovered in the compound in Pakistan where he was killed three years ago.
In the October 2010 memo to a lieutenant, bin Laden advised his men to leave the Pakistani tribal regions where the drone strikes have been overwhelmingly concentrated. Bin Laden wrote, "I am leaning toward getting most of our brothers out of the area" and urged his followers to depart for the remote Afghan province of Kunar, explaining that "due to its rough terrain and many mountains, rivers, trees, it can accommodate hundreds of the brothers without them being spotted by the enemy."
The civilian casualty rate from drone strikes has been dropping dramatically in recent years. According to New America Foundation data, the casualty rate in Pakistan for civilians and also for "unknowns" -- those who were not identified in news reports definitively as either militants or civilians -- was around 40% under President George W. Bush when the drone program was in its infancy. It has come down to about 7% under Obama.
Bergen: Obama's high-stakes drone war in Yemen
In 2013 in Pakistan and Yemen, the numbers of civilians killed by drones in both countries combined was the lowest ever, in the single digits, according to the New America Foundation's data.
This shift has been accomplished because of the combined effects of smaller munitions, improved drone flight technology, better intelligence on the ground, stricter White House guidelines regarding the use of drones, increased congressional oversight of the drone program and greater public scrutiny of the issue.
It will be many years before other countries are able to build up the capacity that the United States has to carry out lethal drone strikes. As of 2013, the United States had drone bases in countries such as Afghanistan, Djibouti and Saudi Arabia. And it isn't as easy as some might think for other nations to arm unarmed drones.
Such weapons systems require specific electrical engineering; the wings must be reinforced for the aircraft to sustain the force of launching a missile; the drone must be equipped with fire control systems, and built-in mounting brackets are needed to attach munitions to the vehicle.
But even with these inherent limitations, the drone industry thrives, and more companies and nations continue to jump on board the drone bandwagon. And the U.S. aggressive and secretive drone campaign against al Qaeda and its affiliates is setting a powerful international precedent about the use of armed drones.
It is these kinds of drone strikes that are controversial since the use of armed drones in a conventional war is not much different, legally, than a manned aircraft that drops bombs or fires missiles.
There has been virtually no substantive public discussion about what an international legal framework governing such drone attacks should be among policymakers at the international level. It's long past due for that conversation to happen.
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