Yes, we know that now, but it wasn't realized in the 1930's. Back then, it was thought to be a viable concept. Like the turret fighter, the heavy escort fighter, hydogen-filled zeppelins, and other failed concepts, it wasn't until it was tested in combat that it was realized to be invalid.
It makes you wonder which modern war-fighting concepts we're training to use will be found invalid when the next war breaks out.
CD