By Paul Wood
BBC defence correspondent
Unmanned robot planes which roam across the battlefield to hunt and kill the enemy are not the stuff of comic books.
The RQ-1 Predator spy plane was developed in the 1990s
They are here, now, and proving so useful that the Pentagon is about to spend $13bn on a new generation of Unmanned Aerial Vehicles (UAVs).
The US and the British militaries are also looking at ways to make these drones invisible - to radar, the naked eye or even to infra-red sensors.
Both governments are spending large amounts on radical ideas about war-fighting.
They believe information will be the deciding factor on future battlefields. And with greater control of information, the theory goes, there will be less need for large, heavily armoured forces.
Up to 800 remotely piloted aircraft are said to be operating in Iraq and Afghanistan, most in Iraq.
The skies are so full of them, there have even been problems with drones crashing into piloted aircraft and helicopters.
The tactical strengths and the weakness of using drones to gather information on the battlefield were seen in last November's assault on the Iraqi city of Falluja.
Pre-war, the US said Iraq used UAVs like this with a 500km range
As tanks, armoured vehicles and infantry gathered in the desert outside Falluja, we watched as two marine intelligence officers started up the motor on what almost looked like a model plane from a toy shop.
With a wing-span about 2m (6ft), they were able to hold it aloft, and launched it simply by throwing it in the air.
A couple of hours later marine commanders were looking at detailed photographs of the streets their troops would shortly assault.
Up to 100 suspected car bombs were spotted in this way. Groups of insurgents were seen massing for ambush.
The precise co-ordinates of ammunition dumps were identified, so that they could be destroyed by artillery.
But the drones could not tell the marines the location of the insurgents' leaders, or even if they were still in Falluja.
The drones could not estimate the total strength of the guerrillas - vital information for the attacking forces.
And they could not see into apartment blocks and mosques to find the individual snipers who were such an effective "force multiplier" for the insurgents.
One remote pilot
Two remote sensor operators
Can carry two Hellfire missiles plus targeting system
Range: 454 miles (726km)
Speed: 135 mph (216 kph)
The danger for modern armies is that the technology is so good it dominates intelligence gathering to the detriment of "humint" or human intelligence.
Certainly, the US military seemed to have very few human sources - informants - on the ground in Falluja.
Nevertheless, the US will spend another $13bn on UAVs by the end of the decade.
This money is being spent not least because the most sophisticated drones do not just gather information - they kill the enemy as well.
Much of the money will go on the best-known of the remotely piloted fleet, the Predator, which is equipped with Hellfire air-to-ground missiles.
The Predator flies as slowly as 80mph (130km/h), and can wait patiently for 24 hours or more at 15,000ft above the battlefield.
It has a zoom lens, radar and infrared sensors and can send live images to troops equipped with special laptop computers.
In Iraq, according to a report in the New York Times, insurgents bury roadside bombs by using burning petrol to soften the asphalt. The Predator's sensors can detect the heat and warn nearby troops.
Predators are also a weapon of choice for the CIA.
Hellfire missiles launched from one three years ago destroyed a car in Yemen, killing a suspected al-Qaeda operative and five other occupants.
The British military is enthusiastic about this new technology. It is reported that an RAF pilot recently became the first member of the British forces to fire a missile from a drone.
This was a United States Predator flying over Iraq - the pilot was said to be operating it remotely from a trailer in the US mid-West.
Britain and the US are both working on "visual stealth", making drones invisible from the ground.
A British programme called Chameleon aims to use fibre-optics and light emitting diodes to diminish the contrast between an aircraft and the sky.
Aircraft stand out against the bright sky as darker objects, but by using bright panels of light, a plane can almost disappear against the blue sky.
British researchers have even been experimenting with technology to electronically alter infrared emissions - to make a warm object appear cold. This device is known as "the infrared chameleon".
However, Falluja was fought with the US marines going street to street, house to house with M16s and a handful of grenades. This may be the pattern for future deployments of British and US forces around the globe.
New technology has its uses, but in such urban combat, there is no substitute for "boots on the ground". The drones will not take over the business of war fighting just yet.