AS A special-forces agent in the French Navy, Michel Malalo has clandestinely entered several African countries by sea to extract endangered French nationals. Almost all the enemy fighters he encountered carried the AK-47, a widely used assault rifle renowned for its rugged reliability. But the AK-47 has a serious drawback: glint, which gave Mr Malalo an advantage in firefights. Made with steel, the AK-47 reflects light. “It's flashy—and from afar,” says Mr Malalo, who took advantage of glint giveaways when shooting at the enemy. Mr Malalo, who left the special forces uninjured six years ago, says the French assault rifle, the Famas, is superbly non-reflective even in bright light.

Developing new metal alloys to reduce rifle glint is just one facet of the effort to develop better camouflage, concealment and deception technologies that is under way at defence contractors, military research bodies and university laboratories. Most of this research is being conducted in America and Europe. Much is classified. The results are often remarkable.

Even the most common form of camouflage—the coloured patterns printed onto combat fatigues—is being given a high-tech twist, as designers work with new software that incorporates neuroscientists' understanding of human vision. Pattern-generation software analyses a large number of photographs of a given theatre of operations. By crunching meteorological data on typical lighting and visibility conditions, combined with information about the colours and predominance of shapes visible in cities, fields and wilderness areas, the software proposes new, improved patterns. “It really does get technical,” says Réjean Duchesneau, a lieutenant-colonel with NATO in Casteau, Belgium, who helped design a Canadian camouflage pattern called CADPAT.

Some camouflage designers, including those at America's Army Research Laboratory, also study the reflective and light-absorbing properties of materials common to an area, such as sand, cement and foliage. As well as being used by the camouflage-generation software, this information is used to manufacture fabric inks with the desired optical properties. Similar software optimises colours and patterns for vehicles and aircraft. The ability to customise camouflage for particular theatres has increased the use of temporary camouflage, which is painted on hardware before missions and washed off afterwards.

For decades most fatigues, now referred to as battledress uniforms, incorporated wiggly patterns of solid colours known as tiger stripes. But research in the field of “clutter metrics”—the study of how well observers locate and identify objects—has recently discredited tiger stripes. With the help of eye-tracking devices that follow iris movements to determine where subjects are looking, researchers have determined that fabrics with small squares of colour, known as pixels, are harder to see. These new pixel patterns are now worn by many Western armies, including those of the United States, Britain, Canada, France and Germany. Canada has improved its camouflage so much in recent years that to spot soldiers in some conditions, observers must be 40% closer than they would have to have been in 2000.

“Adaptive” camouflage that changes rapidly in response to the environment is also in the works. TNO, a Dutch defence contractor based in Soesterberg, is using thin, textile-like plastic sheets embedded with light-emitting diodes (LEDs). A small camera scans the environment, and the colours and patterns displayed on the sheet are changed accordingly. The material is not yet flexible enough to be worn comfortably by soldiers, but it is being tested in Afghanistan with Saab Barracuda, a Swedish maker of camouflage equipment.

Pieter Jacobs, TNO's chief technologist, says the defence ministries of Canada, Germany and the Netherlands, which have funded the development of the technology, consider such “chameleon” sheeting to be an urgent requirement. Maarten Hogervorst, a vision neuroscientist at TNO, says its performance is formidable. A tank draped with the sheeting and parked in front of a grassy slope displays an image of grass on its exposed side, for example.

Another kind of adaptive camouflage is based on flexible plastic decals. A small camera, powered by a solar cell, senses the colours and patterns of the surroundings. The surface of the decal is a crude computer display which then replicates these colours and patterns. The US Army wants to use this approach to wrap artillery and munitions containers. Daniel Watts, who leads the project at the New Jersey Institute of Technology (NJIT), says it works well but is still too expensive for battlefield use.

Some like it hot

Concealing things on the battlefield does not just mean hiding them visually. A lot of research is also being done to reduce thermal signatures, too. Infra-red and thermal-vision equipment can reveal a soldier's heat signature at a large distance. Such equipment is becoming less expensive and is now so readily available that the Taliban in Afghanistan are well equipped with it—unlike a few years ago, says Hans Kariis, a senior technologist at the Swedish Defence Research Agency, a government body in Stockholm.

Fabrics designed to block human heat-signatures are improving rapidly. John Roos, a retired US Army colonel in Newport News, Virginia, recently observed a night-time test of an infra-red “stealth” poncho developed by AAE, a small defence contractor based in Fullerton, California. It was the most impressive infra-red protection he had seen. The man disappeared like “a black void”, Mr Roos says. (The head of AAE, Rashid Zeineh, declined to discuss the fabric's composition.)

America's existing heat-blocking garments already provide a remarkable combat advantage, says Mr Roos. They are similar, but inferior, to the AAE stealth poncho, he says. During some night operations, American soldiers may be heard approaching while remaining concealed in the dark. “You can imagine what that would do to enemy morale,” Mr Roos says.

One way to block body-heat signatures is to use particles called cenospheres—tiny hollow spheres of aluminium and silica that can be woven into fabrics. A leader in the field, Ceno Technologies, in Buffalo, New York, is developing a cenosphere body-paint for the face and hands which does not block necessary perspiration. Britain's Ministry of Defence is testing it.

Researchers at the NJIT, meanwhile, have developed insulating decals that can be applied to hot objects—even firing artillery cannons—to mask their heat signatures. Even if the heat signature cannot be concealed entirely, decals can be placed so that they alter the signature's shape. Mr Watts says his team has been successful in partially insulating tanks so that observers with night vision see the shape of a car.

 Illustration by Derek Bacon

This is a useful trick, because entirely eliminating a vehicle's heat-signature can be extremely difficult. Intermat, a Greek supplier of concealment materials to defence contractors including British Aerospace, Lockheed Martin and Thales, produces a foam coating that also smothers heat signatures. Bill Filis of Intermat says that selectively applying a one-centimetre layer of heat-insulating foam can make an armoured personnel-carrier resemble a motorcycle when viewed through thermal-vision goggles. “Make him wonder, and this buys you time,” Mr Filis says.

Some thermal coatings are as thin as a coat of paint, so they can be applied to aircraft. But warplanes present an additional problem. When flying high to avoid anti-aircraft fire, white condensation trails, or “contrails”, can form “a giant arrow in the sky pointing to where the plane is,” says Charles Kolb, chief executive of Aerodyne Research in Billerica, Massachusetts. Researchers at the firm, which is a contractor to America's air force, are examining the thermodynamic processes that lead to the formation of contrails, in the hope of reducing them using chemical additives.

Even as people, weapons and vehicles become harder to spot, however, new detection technologies are also being developed. In the spring of 1999 NATO warplanes flew more than 38,000 sorties over Serbia, in a bombing campaign that succeeded in pushing Serbian forces out of Kosovo. But surprisingly little damage was done to Serbian materiel. Duped NATO pilots had destroyed dummy tanks, artillery and other items of military hardware made out of wood and tarpaulins. Much of Serbia's real military kit was hidden safely under foliage, which interferes with standard radar.

Engineers at Lockheed Martin, a large American defence contractor, have designed a radar system called FOPEN, short for foliage penetration. It became operational in 2005, but still requires further development and is deployed on just one active American warplane so far. But Lockheed Martin's FOPEN programme manager, Robert Robertson, says the radar “will see whatever man made” under a leafy triple canopy, or under netting designed to foil conventional radar systems.

“Stealth” aircraft, designed to avoid detection by radar, have been around since the 1970s. Radar systems illuminate the target with radio waves and then look for reflections, so absorbing incoming radiation, or deflecting it in a totally different direction, can shrink an aircraft's radar signature dramatically. Half a dozen countries now build stealth aircraft, at great expense.

A new type of radar system, however, is capable of spotting such aircraft. It relies on the proliferation of mobile-phone signals. When a plane flies through an environment filled with such signals, the “aircraft shadow in this chatter” becomes visible, says John Pendry, a radar expert at Imperial College in London. Mike Burns, the president of MSE, a small defence contractor in Billerica, Massachusetts, says stealth bombers have indeed been detected against backgrounds of mobile-phone radiation because “a hole” appears in the constant chatter of signals.

This technique can be used only in populated areas, with lots of mobile phones. But it has an edge over standard radar, in addition to being able to spot previously invisible aircraft. It is “passive”, because it uses ambient radiation to illuminate the target. This means the target aircraft cannot tell that it is being watched (whereas it can with traditional radar). In short, it is the radar-detection system, rather than the aircraft, that has become invisible. It is just the latest example of the arms race between concealment and detection.