BAGHDAD, Iraq -- The lumbering, low-tech observation balloon, first used on Civil War battlefields, is making a comeback in Iraq. But this time around it's packed with zoom-lens video cameras and thermal imagers.
The unmanned craft -- which looks like smaller versions of the Goodyear blimp -- monitor battle zones and other danger spots. They're also used to detect possible ambushes on roads used by multinational forces.
On a recent evening in Baghdad, three balloons floated over the Green Zone that houses Iraq's interim government, as well as the U.S. and other foreign missions in central Baghdad.
They have also been seen circling dangerous highways leading to Baghdad International Airport, where car-bomb attacks against U.S. troops have become a daily occurrence. And during last month's U.S.-led offensive against the rebel-held city of Fallujah, a balloon hovered constantly over the battlefield.
"They are on a tether and can be relatively easily moved to any area required," U.S. military spokesman Maj. Jay Antonelli said.
While the gleaming white balloons are hard to ignore, Antonelli was reluctant to discuss all they can do. "I cannot disclose their capabilities for force protection reasons," he said.
The balloons' payload typically consist of an array of high-tech sensors, including a video camera with a zoom lens, a thermal imager or a laser range finder, a U.S. official said on condition of anonymity. The devices mainly look for muzzle flashes from small arms or mortars or try to spot suspicious movements by potential attackers.
While the balloons might appear to be easy targets themselves, they are more likely to survive hostile fire than fixed-wing drones.
Unlike World War I balloons -- which were filled with highly flammable hydrogen -- today's craft contain helium, an inert gas that doesn't burn. That means ground fire only causes slow leaks and a very gradual loss of buoyancy.
Observation balloons were first used during the Civil War, when the Union and Confederate armies sent officers up in wicker baskets to direct artillery fire at opposing troops.
Their usage by artillery spotters peaked during the trench warfare on the western front in World War I, but the balloons largely faded from use soon after due to the ascendancy of fixed-wing biplanes, though some remained in service for several more decades.
The U.S. Navy withdrew its last blimps from service in 1962 after years of using them for ocean patrols.
During the last decade, however, robotic spy balloons equipped with high-tech optics systems began to reappear. They primarily have been used by the Israelis to track the movements of militants and by the U.S. Border Patrol to monitor illegal immigrants crossing the Mexican border.
Surveillance balloons, also known as aerostats, were introduced into U.S. service in Iraq earlier this year, after it became clear they had inherent advantages over the unmanned drones that provided battlefield intelligence during the U.S. invasion of Iraq in 2002.
Front lines change quickly or don't exist at all in the battle with insurgents, who appear in order to fire mortar shells or plant explosives before melting into the background.
Balloons can loiter over a military base or likely ambush site to discourage such strikes. Or they might accompany foot and vehicle patrols, spotting potential targets from several miles away.