This is a short story I remember reading in some anthology many years ago. The basic plot is that a nuclear adversary of the USA (it might have been China), lacking the necessary missile technology, instead delivers its nuclear weapons to multiple US cities by cargo truck. Once in place, they are all detonated with devastating effect, allowing the adversary to invade and conquer the smouldering remains of the US. I was reminded of this story by recent world events. However I've not been able to identify the story, which I think dated from the 1950s or thereabouts, or recall who the author was. Can anyone help?