I was involved with the first C-130A models 1956. I think it was the first operational turbo prop aircraft. When I saw the engines it was hard to believe the thrust. It was only about two foot long. My prior experience was with the 28 cylinder R4360 recip engines common to big bombers and transport aircraft. In 1958 a C-130 “disappeared” on a cross country flight. It turned up long after it would have run out of fuel. It was reported that it had simply shut down two engines and kept on flying.
Britain had turbo prop aircraft before 1956, such as the Vickers Viscount.