The F-84 was a product of the US Army Air force request during late WW2 for a jet fighter. The Republic company was one of the contenders. Initially they studied placing a jet engine into a P-47 Thunderbolt. But that turned out to be a bad concept. So they decided on a clean sheet design. Thus the F-84 was developed into a slick very thin fuselage with straight wings. It was ready to fly two years after the end of the war ( in 1947 ). It competed against the Lockheed P-80 and the North American F-86. As it turned out the Army Air Force allowed production to all three aircraft. However, the straight wing of the F-84 and the P-80 were already obsolete and inferior to the Swept wing F-86 Sabre. So the next step was to design a swept wing version. That has become the F-84F Thunderstreak. This aircraft was also distributed widely to all NATO forces and that is why it became a recognizable aircraft.
more reading here:
https://en.wikipedia.org/wiki/Republic_F-84_Thunderjet
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