On a more peaceful note, the device would also be used to turn the Arctic and Antarctic poles into verdant gardens. Via io9:
In 1945, Life magazine revealed how “U.S. Army technical experts came up with the astonishing fact that German scientists had seriously planned to build a ‘sun gun’…a gigantic orbital mirror that would “focus the sun’s rays to a scorching point on the earth’s surface.” The German army, readers were told, “hoped to use such a mirror to burn an enemy city or to boil part of an ocean.”
The idea had been originally proposed by the seminal rocket scientist Hermann Oberth in 1923. Oberth thought it might take ten to fifteen years to assemble a complete mirror at a cost of $3 billion. The pressure of sunlight on the vast surface would be used to maneuver it in orbit, with steering accomplished by adjusting the angles of the individual mirrors.