For example, Britain had a theory of radar by the late 1920s, radar itself in much of the 30s, and airborne radar by 1937.
Knowing the theory behind a new technology is all well and good, but more important is what you do with it and how you develop it. As an example, in late 1944, the IJN had shipboard radar on most, if not all of its capital ships and some of its smaller ones. This could show an enemy fleet as separate squadrons, but couldn't resolve those squadrons into individual ships and they were just beginning to experiment with using radar to aim their guns. The USN had radar on most, if not all of its fleet, it was sharp enough to show squadrons as individual ships and it was routine to use it at night for fire control, as the Japanese learned the hard way. I'm sure I could find other examples if I put my mind to it, but I think I've made my point clear.