The U.S. military's successful deployment of drones in combat provides a glimpse into the future of warfare. Without putting any U.S. pilots in danger, drones can deliver precisely targeted, highly lethal strikes on enemy personnel.

A drone is an example of a semi-autonomous weapon system; the command to fire the drone's weapons is made by a human on a military base in the U.S. The U.S. also uses semi-autonomous weapons to launch Patriot missiles in its air defense systems that guard the coasts against enemy missiles and airplanes, and on board Navy ships.

Another example of a semi-autonomous weapon system already in use is the Samsung SGR-A1 Sentry robot that South Korea uses to guard its border with North Korea. It is equipped with heat and motion sensors to detect activity up to two miles away. According to the U.K.'s Daily Mail, each Sentry can fire a 5.5mm machine gun and a 40mm grenade launcher. When it identifies a potential attacker, it alerts the command center, where a human operator can use its audio function to issue a warning or give the command to fire its weapons.

These weapons are just the first generation of a new arsenal of powerful machines that will at first work side by side with soldiers, and eventually replace them. Many of the projects remain classified, but the U.S. military and defense contractors-as well as the governments of U.S. allies and potential enemies-have revealed prototypes of several robots that can be used for surveillance, support, search and rescue, bomb detonation, and combat.

While some of these new weapons are semi- autonomous, others are fully autonomous-meaning they can respond to a threat without waiting for a human to make a decision. The Department of Defense defines an autonomous weapon system as "...a weapon system that once activated, can select and engage targets without further intervention by a human operator."

While the U.S. is the undisputed leader in military robotics technology, Russia and China are now in the race. Let's take a look at the next generation of military robots and tactics:

• On land, the U.S. Defense Advanced Research Project Agency (DARPA) has revealed two applications for using autonomous weapons in urban combat environments. As explained by Stuart Russell, Professor of Computer Science and Engineering at the University of California, Berkeley, "The Fast Lightweight Autonomy program will see tiny rotorcraft maneuver unaided at high speed in urban areas and inside buildings.
  
  The Collaborative Operations in Denied Environment program plans to create teams of autonomous aerial vehicles that could carry out every step of a strike mission in situations where enemy jamming makes communication with a human commander impossible."
  
• In the sky, DARPA is also testing the concept of a drone aircraft carrier that would be based in the air rather than on water. Like a mothership, it would launch smaller drones for surveillance and aerial attacks.
  
• On the sea, the U.S. Navy is developing drone speedboats that could follow an enemy ship and then attack it either autonomously or by following remote-controlled instructions.
  
• DARPA has also been developing advanced humanoid robots. According to the U.K.'s Daily Mirror, "One such robot is Atlas, a 6'2" machine that walks on two legs and is designed-at least for the time being-for disaster relief. It's not hard to imagine swapping out Atlas's arms for guns and turning him into a terrifying foot soldier."
  
• In the private sector, Google subsidiary Boston Dynamics has invented the RHex, a compact remote-controlled six-legged robot that can climb stairs or traverse swamps. It is equipped with night vision for surveillance missions. Boston Dynamics also developed BigDog, a robot that resembles a dog or mule that can haul equipment. According to TheVerge.com, Big Dog can race across a battlefield on four legs at four miles per hour, climb over rocks, and pick up and throw cinderblocks.
  
• QinetiQ has developed the Modular Advanced Armed Robotic System (MAARS). MAARS looks like a small tank. According to Wired.com, it can be equipped with night vision, motion sensors, a machine gun, and four grenade launchers.
  
• iRobot, creator of the Roomba floor-vacuuming robot, is also turning its attention to military robots. The company's site explains that, "More than 5,000 of the company's defense & security robots have been delivered to researchers, military and civil defense forces worldwide, performing thousands of dangerous search, reconnaissance and bomb-disposal missions while protecting those in harm's way." For example, the 710 Kobra detonates bombs while the human operator maintains a safe distance, directing the robot with a touchscreen app.
  
• Israel Aerospace Industries has introduced RoBattle, an unmanned robotic military vehicle that can work autonomously or by remote control. According to the company, "The system is designed to be integrated with tactical forces in mobile, dismounted operations and support a wide range of missions including intelligence, surveillance, and armed reconnaissance, as well as convoy protection, decoy, ambush, and attack."
  
• Russia has announced that its Foundation for Advanced Studies-Russia's version of DARPA-is working on "Iron Man" or "Ivan the Terminator," a humanoid robot soldier. According to Russian newspaper Pravda, "The development of a special military robot is one of the priorities of military construction in Russia." Vice.com reports that the Foundation is also working on aerial drones as well as tank drones. It also has a remote-controlled robot called the Uran-6 that is used to detonate land mines, and the Uran 9, which can fire 400 bullets per minute.
  
• China recently introduced its own military robot, AnBot, at the Twelfth Chongqing Hi-Tech Fair. The AnBot is nearly five feet tall, weighs 171 pounds, and can move at eleven miles per hour. Developed by China's National Defense University, the AnBot is designed to quell rioters and protestors by zapping them with electric shocks. China's other robots include an "attack robot" that can fire rifles and launch grenades.

While the technology for military robots is advancing rapidly and they provide a way for the military to offset the declining demographics of OECD countries, obstacles to their deployment still exist. U.S. government policy currently allows only the development of non-lethal autonomous systems. Lethal autonomous systems are officially forbidden until 2022; any weapons system in use before then must include a human operator "in the loop" before deadly force can be used against humans. However, autonomous systems can be used to destroy unmanned targets, such as drones or missiles launched against military bases, planes, or ships.

But even if the U.S. reversed its policy, international policies prohibit the use of lethal autonomous weapons, and the resistance to their use is growing. For example, according to the Hague Convention, any combatant must be "commanded by a person."

The Secretary General of the United Nations, Ban Ki-moon, has called on international experts to create a policy regarding the use of autonomous weapons systems proactively.

A coalition of human rights organizations has started a "Campaign to Stop Killer Robots." It includes nearly three hundred scientists from thirty-seven countries who have demanded a ban on the invention and use of fully autonomous weapons.

In 2015, more than 3,000 experts in artificial intelligence and robotics research signed an open letter calling for a treaty to ban lethal autonomous weapons. Another 17,000 experts from other fields, including Stephen Hawking, Elon Musk, and Steve Wozniak, also signed the letter.

Several countries have vowed to keep humans in control of their military weapons. For example, Britain's Parliamentary Under Secretary of State at the Ministry of Defense has declared, "let us be absolutely clear that the operation of weapons systems will always be under human control." Germany has said it "will not accept that the decision over life and death is taken solely by an autonomous system."

There are at least two reasons why people fear autonomous weapons systems. One reason is that such systems lack human reasoning and empathy. If one of South Korea's SGR-A1 Sentry robots automatically opens fire on any intruders it detects crossing the demilitarized zone from North Korea, it could potentially kill a family of refugees seeking freedom, or an enemy soldier attempting to defect to the West.

The other reason that autonomous military robots inspire fear is the possibility that humans will lose control of them.

Russell, the Berkeley professor mentioned earlier, recently asserted in a World Economic Forum Agenda article that "Autonomous weapons in conflict with other autonomous weapons must adapt their behavior quickly, or else their predictability leads to defeat. This adaptability is necessary but makes autonomous weapons intrinsically unpredictable and hence difficult to control." He concludes, "At present, the public has little understanding of the state of technology and the near-term possibilities, but this will change once video footage of robots killing unarmed civilians starts to emerge. At that point, the dictates of public conscience will be very clear but it may be too late to follow them."

Using autonomous and semi-autonomous systems also threatens to eliminate the valuable experiences that turn junior officers into future leaders. The need to make split-second battlefield decisions today is essential to the development of tomorrow's generals. But if machines make those decisions, the U.S. could face a leadership vacuum.

Currently, no countries have used fully autonomous lethal robots. But what lies ahead? Please consider the following forecasts:

First, by 2025, the U.S. will have developed all of the necessary technology to deploy fully autonomous lethal robots.

That prediction comes from Major Daniel Sukman, a U.S. Army Strategist who has served three combat tours in Iraq. He asserts that military robots will transform the way that America fights its wars, and that the impact of autonomous weapons systems will be as important as gunpowder, mass conscription, and nuclear bombs. There is no limit to the number of robot soldiers that can be deployed. However, international policy will constrain their use.

In the Canadian Military Journal, Sukman explains that "International policy trends indicate that nations may prohibit the use of autonomous lethal weapons systems and robotics on the battlefield in the future." The U.S. may choose not to sign an agreement to ban such weapons, just as it has refused to sign an international ban on landmines in order to allow the DMZ to be mined between North and South Korea, because hostile governments and terrorist groups will not adhere to any such agreements. The fact that Russia and China are pursuing their own military robotics programs means that the U.S. will need to continue to invest in autonomous weapons systems in order to maintain its military superiority.

Second, military robots will enable the U.S. to lower the financial and human costs of warfare.

As much as 25 percent of U.S. troops could be replaced by robots and remote-controlled military vehicles. According to Popular Science, General Robert Cone told an Army Aviation symposium that the Army is evaluating whether to use drones and bots to reduce its Brigade Combat Teams from 4,000 soldiers to 3,000.11 That would enable the Army to reduce its casualties, and to cut by one-fourth its costs for recruiting, training, and feeding soldiers, as well as medical costs both during their active duty and afterwards.

Third, whether they are remotely controlled or fully autonomous, robot soldiers will not be limited by human emotions like empathy.

The risk is that dictators could use them against civilian populations in other countries, or even in their own homeland. For example, Russia could sell robots to Syrian President Bashar al-Assad, who would not need to coerce Syria's human soldiers into killing civilians who oppose his reign. According to artificial intelligence expert Peter Asaro, a spokesman for the Campaign to Stop Killer Robots, "They are going to go to tyrannical dictators who often have trouble convincing their militaries to attack their own people, which we saw in Egypt. The military refused to attack people in Tahrir Square." Humanoid robots could simply be programmed to slaughter any humans they encounter within a certain timeframe or geographic range.

Fourth, military robots will increasingly replace police officers, DEA agents, and firefighters in dangerous situations.

In July 2016, the Dallas Police deployed an Andros F5 military robot made by Northrop Grumman's subsidiary Remotec to kill a gunman who had shot several police officers. According to the department's official statement, the F5's arm clutched a pound of the explosive C4 when it approached the suspect, and officers used a detonation cord to trigger the fatal blast.

A report on the tech site Gizmodo cited experts who said it was "the first lethal use by a civilian police force of a military bomb robot." Another Gizmodo report notes that the F5 is an earlier model of the current Andros 56B bomb-disposal robot, which can carry up to sixty pounds.14 Clearly, a robot equipped with sixty pounds of C4 could create extensive damage and countless casualties-which means it will be vital to prevent their sale to terrorists.

Fifth, it will remain unclear for some time which firms will emerge as major players in the military robotics field.

For a while it looked like Google would take the prize. But, its acquisition of Boston Dynamics for $500 million as well as several other robotics companies in recent years has had mixed results. The company established itself as an important defense contractor through the BigDog and RHex programs.

Google seemed poised to create synergies since it's already the leader in autonomous vehicle technology for civilian uses. Unfortunately, it has been unable to integrate the culture of Boston Dynamics with the rest of its business and now plans to sell it. However, it is still reasonable to assume that it could apply what it has learned about designing driverless automobiles to create autonomous tanks and other weapons systems.

Sixth, military robotics research will enable big leaps in the performance of civilian robotics.

Just as the Internet, jet aircraft, helicopters, integrated circuits and satellites were all originally developed for defense, today's military robots will underwrite the R&D required to create a transformational wave of cost-effective civilian service robotics. Today's cyber-warrior may give birth to the eldercare robot of 2025.