In 1935, British engineer Robert Watson-Watt was working on a 'death ray'‚ that would destroy enemy aircraft using radio waves. His death ray instead evolved into RADAR.
In the early 1930s, Great Britain found itself in a rather precarious position. Military theorists were predicting, quite correctly, that the next war would be dominated by airpower and the ominous threat of aerial bombardment. With Nazi Germany on the rise, the Brits suddenly felt very vulnerable. To address the problem, Britain launched a number of projects in hopes of mitigating the threat — including an effort to develop nothing less than a high-tech "death ray" that could shoot enemy planes out of the sky.
But even though the project failed to develop such a weapon, it did result in something potentially far more useful — a technological breakthrough that would prove to play an integral role in the British victory over the Nazis during the Battle of Britain.