Józef Kosacki, a lieutenant in the exiled Polish army, designs in 1941 the Polish Mine Detector, the first portable mine detector in history: an electromagnetic induction device that detects buried metal objects via headphones. He builds it secretly in Edinburgh with locally available materials and hands it over, without patent or compensation, to the British army. Kosacki's detector was used massively at the Battle of El Alamein (1942), where it allowed minefields to be cleared in the Libyan desert and contributed decisively to the Allied victory. The British army manufactured 500 initial units and then millions. Kosacki gave up the invention without receiving official recognition or financial compensation; he died in 1990 with his name appearing in no Allied museum or monument.