The U.S. deployment of attack drones in the tense Korean theater is a symbol of not only the role unmanned aircraft are playing in the so-called war on terror, but a sign of a rapidly evolving and increasingly competitive defense market dependent on robot warfare.

Business, as they say, is booming. Jane's Defense is forecasting that the world's militaries will spend $82 billion based on a forecast of 63,000 military drones being sold in the next 10 years.

“It’s a really crowded marketplace,” said Dan Wasserbly, an analyst at IHS Jane's/IHS Markit (NASDAQ:INFO). “Everybody makes these things now."

At least 140 specific models of drone are used by the world’s defense agencies for either surveillance or to take out human and other ground targets, according to the Military Factory, with the U.S. using them heavily in Afghanistan and Iraq. Though there are philosophical arguments against using these killer robots, it’s clear drone warfare is ingrained in global defense budgets of all sizes.

2 Military Vendors Hold Half Of Drone Market

The long-endurance Gray Eagle drones being deployed in South Korea are manufactured by the privately held General Atomics Aeronautical Systems, Inc., the leading military drone contractor, though some engines and armaments are provided by publicly traded companies. The Gray Eagles carry the potent, armor-penetrating Hellfire missiles produced by the Lockheed Martin Corporation (NYSE:LMT).

General Atomics, Northrop Grumman Corporation (NYSE:NOC), Textron Inc. (NYSE:TXT) and Boeing Co. (NYSE:BA) account for 66 percent of the drone market, according to the defense intelligence journal C4ISTNET. It said that General Atomics’ MQ-9 Reaper — powered by a Honeywell International Inc. (NYSE:HON) engine and a Raytheon Company (NYSE:RTN) targeting system — accounted for more than a quarter of the defense drone market.

Anti-Drone Defense: A Growing Sector 

The increased reliance on drones likely will lead to attempts by competitors to break into General Atomics lion's share of the market, said Philip Finnegan, director of corporate analysis for the Teal Group, a defense and aerospace analytical firm.

One of the big growth sectors in the drone defense business is developing anti-drone defense systems to deal with the deluge of small drones that can be used for guerrilla warfare. The radical Islamic State in Iraq and Syria have perfected the use of drones for surveillance and is seeking to weaponize them.

Wasserbly said it wouldn't be a good investment to use a missile to down a drone, since many are so cheap and small.

Boeing and Northrop Grumman are developing systems for truck-mounted laser guns for the U.S. Army, Wasserbly said. The nonprofit Battelle Memorial Institute makes the “DroneDefender,” which shoots radio frequencies to confuse enemy drone’s GPS systems.

“It looks like a really impressive rifle,” Wasserbly says.

The Teal Group's Finnegan said drone counter measures are vital.

"There's going to be explosive growth in that area," he said. "It is going to be huge."

Billions At Stake

The Teal Group's latest study estimates that military unmanned aircraft will rise from a $2.8 billion business in 2016 to $9.4 billion in 2025. The civilian, local government and commercial side has perhaps even more potential, with Teal forecasting the $2.6 billion in sales last year reaching $10.9 billion by 2025.

Business Insider predicted overall U.S. drone revenues — both military and commercial — would reach $12 billion by 2021 compared to $8 billion in 2015.

The degree to which a reliance on aerial robots will render existing manned systems obsolete is unclear. Though drones have replaced some attack helicopters, Wasserbly said unmanned systems are more “supplemental” to global defenses.

The U.S. military has for years used unmanned vehicles and vessels to combat mines, and advanced robotics in those areas are expected to also grow.

"Unmanned military ground, sea and air vehicle technology is evolving rapidly and we are seeing strong growth across all three sectors over the next five to ten years," said Derrick Maple, principal analyst for unmanned systems at IHS Jane's.