Now you see me, now you don't. From the simplicity of a camouflaged uniform to the complexity of a real-life invisibility cloak, armies have long used smoke and mirrors to confuse the enemy and retain an element of surprise.

The first heat-seeking weapons were developed in the 1950s. It wasn't long before the U.S. military started to look for ways to hide heat and protect themselves from missiles. They came up with the idea of using metallic dust clouds called obscurants, which are still deployed today. The trouble is obscurants aren't exactly environmentally friendly. They're also pretty difficult to control.

That's why the Army has just handed out financial awards, somewhere in the region of $100,000 each, to three private companies in the hopes that one of them might develop a better obscurant. Lynntech, Inc., Nanotrons, and Physical Sciences are each about to begin product development.

Tanks, planes, and other large pieces of military hardware emit infrared radiation, which allow heat-seeking missiles to track their location. But there are ways to keep those signatures low. When surrounded by obscurant particles, the infrared shadow disappears into what is quite literally a fog of war. You might be surprised to learn how these obscurants are deployed; "to block infrared, you fill a grenade with bronze flakes and detonate it" near the object you want to hide, Physical Sciences' John Lennhoff tells Danger Room. The obscurant works by scattering or absorbing the infrared light, meaning that the object is no longer visible to heat-seeking technologies.

Most of today's obscurants are typically made from commercially available metal particles – usually bronze – which are poorly defined in terms of size and therefore difficult to control in application. In addition to this, according to the Army's own award proposal, current obscurants have "significant environmental persistence that may pose health hazards" – yikes.

The EPA says that too much copper – bronze's main ingredient – in drinking water can cause gastrointestinal health problems in the short term, and more seriously, liver and kidney damage in the longer term. One of Lennhoff's aims is to create a new obscurant particle that protects U.S. soldiers but at the same time doesn't pose potential health threats to civilian populations.

If talk of an environmentally friendly, Harry Potter-esque invisibility mist seems too ridiculous for military use, then you obviously haven't heard of deceit pour l'armée, the new fragrance by the Islamic Republic of Iran. Last month, an Iranian news network reported that an Iranian inventor had developed something called "deceit perfume." It disguises the smell of gun powder, which might otherwise alert Iran's downwind enemies of their presence – don't laugh, it's said to be highly effective for surprise attacks.

Or what about the British Illusionist Jasper Maskelyne? In Egypt during WWII he (allegedly) recreated a second Alexandria a few miles up the coast from the real city, where the Royal Navy's Mediterranean headquarters were located. He copied the street lighting grid to match Alexandria by night and extinguished the real city's lights, so that the German Luftwaffe's efforts were wasted in destroying nothing more than a huge hoax. The Brits even went out the next day with fake craters painted on canvases so that the reconnaissance planes, which came the following day, would report back that the mission was a success. At least, that's how the legend goes.

The military has had to focus on reducing hardware heat signatures for the last 60 years. Some have exhaust systems to cool fumes before they're emitted and some planes shoot flares to distract missiles heading their way. But when better obscurants are developed, the military may be able to glide across the battle field in an eco-friendly fog of war, without the fear of their infrared emissions giving them away.