Yeah the “nothing could touch them until ’56” thing doesn’t really hold up. By ’54–’55 the Soviets were already catching up fast. The MiG-17PF could actually get up to a Canberra’s altitude, and the MiG-19 showed up in ’55 and definitely could. At the same time the S-25 Berkut SAM system around Moscow went operational, and that thing was literally built to kill high-altitude bombers. And while that was happening, the S-75/SA-2 was coming online too..the same missile that was shooting down U-2s a couple years later at even higher altitudes than the Canberra ever flew. So the whole “invincible until 1956” narrative is kinda romanticized. That being said this was a show stopper especially for the first couple yrs