THE four-legged beast stalks with feline grace through the shadows. Eyes glint in the darkness. Its superior vision picks out the forms of enemy soldiers advancing. Then, the robot opens fire.

It's not science fiction. It's on the brink of being fact.

This is a scenario soon to be seen on battlefields around the planet: A large container is parachuted into a "hot zone" amid a squad of human troops.

On the ground, the crate collapses open to reveal a mechanised monster ready and armed for action.

Ranging ahead of the troops, the robot will be obeying the commands of its human controllers tucked away safely at the unit's rear.

By taking the risky "point" position, the robot will use its advanced sensors and metallic body to help protect the soft skin of the humans following it.

And if you think this sounds like something out of a sci-fi movie, you should see what the next generation of soldiers will be lugging around.

They will be virtually indistinguishable from their metallic comrades, covered as they are by armoured plates, electronics and even artificial muscles.

The world can expect a dramatic shift in the appearance of those manning their armies as soon as 2015.

A taste is already out there: Black face-hugging "ski-masks" to protect the wearer from close-range bullets and shrapnel, "smart" hand grenades and bullets that track their targets and pocket-sized generators to power the ever-expanding digital network beaming information direct to a soldier's eyes and ears.

The battery is already a soldier's best friend and worst headache.

But perhaps that is a problem will be alleviated by their new metal-and-plastic pals.

media_camera Star Wars combat droid, meet PetMAN. This humanoid robot is currently capable of climbing stairs and crossing rough ground. Soon, it may be fighting fires on ships and helping at earthquake sites.

While the two-legged, two-armed autonomous robots of Star Wars and Terminator may be a decade or so off yet, a wide variety of multi-limbed, tracked and wheeled combat robots are on the brink of being actively deployed.

Some have even been field tested.

Exactly what these armed robots will be capable of was put on display during a life-fire demonstrations in the US in ercent months. Today, the defence research agency DARPA released video showing a mechanical "mule" working with a squad of soldiers.

They come with as many weirdly wonderful names as they do shapes: CaMEL, SWORDS, ATLAS, WildCat and PETMAN to name a few.

media_camera Dr Whos K9, meet CaMEL: These shopping-cart sized tracked robots are chose to being deployed. They are capable of being configured for carrying equipment, wounded soldiers or weapons.

One recent defence demonstration involved Northrop Grumman's wheeled CaMEL. Put through its paces with a M240 machinegun, the robot used its thermal-imaging sights to expose concealed "enemies" before opening fire.

"They're not just tools, but members of the squad. That's the goal," Lt. Col. Willie Smith, chief of Unmanned Ground Vehicles at Fort Benning, told ComputerWorld. "A robot becoming a member of the squad, we see that as a matter of training ... I think there's more work to be done, but I'm expecting we'll get there."

While the US Army and US Marines are not yet willing to say exactly when combat robots will be deployed with its troops, expectations are that it will be within five years.

"We've been looking at robots for years," Smith said. "They save soldiers' lives. Robots can do things like investigate IEDs."

But it's not all chrome and polish.

media_camera Terminator, meet ATLAS: The ATLAS project is making inroads into fully flexible two-legged robots that can maintain their balance and operate equipment.

Many challenges still exist, such as mobility and endurance. "You need it to go where you go," Smith said. "And there's security. You need to protect it from being taken by the enemy or having its weapons system taken."

One program, SWORDS, a tracked robot carrying a heavy machinegun, was reportedly axed after the machine demonstrated having something of a mind of its own by moving about without specific orders to do so.

Not all robotic roles will be slugging it out on the front line.

The US Defense Advanced Research Projects Agency (DARPA) is actively investigating the use of robots in lugging supplies at airfields and depots, as well as taking over sentry duties at forward bases. Others will be used to haul ammunition to embattled troops and evacuate the wounded.

media_camera Star Wars ATAT, meet BigDOG: Robotics firm Boston Dynamics is developing a range of four-legged robots designed to move fast over rough, steep terrain.

The US Navy is examining the potential of humanoid robots to be included as part of a warship's crew specifically tasked to battle dangerous fires and other explosive.

It's a race against time.

In December, the DARPA Robotics Challenge will set competing designs a series of eight tasks to evaluate their potential in emergency situations such as crossing rough ground, using tools and even driving vehicles.

So who are the top contenders?

CaMEL: This robot is intended to be something of a jack of all trades. In one configuration it's little more than an automated shopping trolley, lugging supplies over dangerous ground. In another, it's armed and dangerous. Its simple wheeled design is both a benefit and a problem making it cheaper and less complex, but less capable of handling rough terrain.

WildCat: This four-legged machine is designed to bound, gallop and turn in the same manner as an animal. The intention is to create a high-speed ground robot capable of hunting, stalking and killing just like its namesake. The "Cheetah" precursor to this design last year obtained speeds of up to 45km/h. The WildCat does 25km/h.

AlphaDog: Called a "legged squad support system", the AlphaDog is by all accounts a mechanical horse. The four-legged beast of burden is intended to charge over rough terrain to deliver equipment and pick up wounded soldiers. It is just one of a series of "Dog" robots under development.

ATLAS: One humanoid-style robot was recently tested to see if it had "sea legs". The machine was made to walk over rubble and maintain its balance even when sustaining a heavy blow. Others in the Boston Dynamics series, such as PETMAN, have been dressed in combat gear and put through gruelling physical programs.

media_camera The shape of things to come: Future soldier, meet ATLAS a prototype android currently being developed to fill a variety of military and rescue roles.

So is it a case of the rise of the machines?

"We were pleased with what we saw here. The technology is getting to be where it needs to be. It's a start." Smith said.

Originally published as Blood and chrome: The future of war