LAKE FOREST, Calif. – In 1980, Abraham Karem, an engineer who had emigrated from Israel, retreated into his three-car garage in Hacienda Heights outside Los Angeles and, to the bemusement of his tolerant wife, began to build an aircraft.

The work eventually spilled into the guest room, and when Karem finished more than a year later, he wheeled into his driveway an odd, cigar-shaped craft that was destined to change the way the U.S. wages war.

The Albatross, as it was called, was transported to the Dugway Proving Ground in Utah, where it demonstrated the ability to stay aloft safely for up to 56 hours – a very, very long time in what was then the crash-prone world of drones.

Three iterations and more than a decade of development later, Karem’s modest-looking drone became the Predator, the lethal, remotely piloted machine that can circle above the enemy for nearly a day before controllers thousands of miles away in the United States launch Hellfire missiles toward targets they are watching on video screens.

The emergence of hunter-killer and surveillance drones as revolutionary weapons in the wars in Iraq and Afghanistan, and in counterterrorism operations in places such as Pakistan and Yemen, has spawned a multibillion-dollar industry.

Over the next 10 years, the Pentagon plans to buy more than 700 medium- and large-size drones at a cost of nearly $37 billion, according to a Congressional Budget Office study. Thousands more mini-drones will be fitted in the backpacks of soldiers so they can hand-launch them in minutes to look over the next hill or dive-bomb opposing forces.

This booming sector has its roots in the persistence of engineering dreamers who worked on unmanned aviation when the military establishment and most major defense contractors had little or no interest in it.

Before Sept. 11, drones weren’t “on the road map,” said Tim Conver, chairman and chief executive of AeroVironment, which builds drones for the military.

Before 2001, AeroVironment, through various small contracts, sold a drone called the Pointer in small numbers to the military. “Nobody ever really used them,” Conver said.

When the first Special Operations teams went into Afghanistan in October 2001, they brought with them two Pointer systems that they used for low-altitude surveillance. Soon, word was going up the chain that the troops wanted more Pointers for Afghanistan’s difficult terrain. High above them, the Predator and Global Hawk were also proving themselves.

“The Predator is my most capable sensor in hunting down and killing al-Qaida and Taliban leadership and is proving absolutely critical to our fight,” Gen. Tommy Franks wrote in a 2003 Air Force background paper about the war in Afghanistan.

And the drive for drones was on.