The walkie-talkie debuted in 1943 as the first FM portable two-way radio. It was used by the U.S. Army Signal Corps. during World War II.
It weighted 35 lbs., so it had to be worn on a backpack. But all that heft was necessary to give the device a range of 10 to 20 miles. Portable AM radios, though able to be built much smaller, couldn't be used for long-distance communication.