the japanese worked on a microwave beam weapon in WW2, from gizmondo:
"According to documents confiscated by the U.S. military after the war, work on a Japanese death ray began as early as 1939 at laboratories in Noborito. To that end, the researchers developed a high-powered magnetron that could generate a beam of radiation. Physicist Sinitiro Tomonaga's team developed a magnetron measuring 8 inches (20 cm) in diameter with an output rated at 100kW. It's doubtful, however, that this technology could have worked like the death rays of science fiction. Calculations suggested that the beam, if properly focused, could have killed a rabbit over a distance of 1,000 yards, but only if the rabbit stayed perfectly still for at least 5 minutes."