Seeking novel about aliens who conquer and occupy Earth and forbid technological progress

Question

I read this novel (or possibly novella) in the early 1980s in the UK. The paperback was tatty so it may have been published well before that. It was written in English, and I have a feeling the writer was American rather than British.

The scenario was that some aliens closely resembling humans had invaded Earth about a century previously. They had forbidden Earth technology to progress past the stage it was at the time of the invasion. They themselves were technologically superior and possessed faster than light travel. I think the invasion was meant to have happened in the twenty first century, so there were some futuristic things around but daily life was not very different to the twentieth century.

Two details I do remember:

1) There was a half human / half alien with the surname "Winter" who worked for the aliens' equivalent of the Gestapo. It was stated that he was extra zealous in oppressing humans because he was half human himself. (Evidently humans could interbreed with these aliens but I don't remember any discussion of that issue.)

2) At or near the end it is revealed that a century earlier, just before the humans were defeated in the war, they had launched a fleet of just slower than lightspeed warships at the alien homeworld, which only now was coming into range to attack.

I think the ending of the book just left it there, with what the result of this would be undecided.

I have a hazy impression that the predominant colours on the book cover were yellow and grey. Just possibly the title was in a Courier-style serif font in a dark purple colour. I could very easily be completely wrong about the appearance of the cover.

(Note: In the original version of this question I hid the revelation about the human ships that had been travelling for a hundred years behind a ">!" spoiler code. I've decided to reverse that to increase the chances of getting an answer, as not everyone looks under blanked out areas, yet someone might well only recognise the story by that ending. And I've observed that unmarked spoilers are very, very common under the story-identification tag!)

Answer 1

I have found the answer to my own question, having finally thought to ask the massive science fiction fan with whom I have lived for decades. He didn't immediately know either, but between us we found enough clues to track it down.

The book is The Patient Dark by Kenneth Bulmer. It seems to have been originally published in 1958 under the title The Secret of ZI, then republished under the "Patient Dark" title in 1969. I have just now bought it on Kindle but have not read (or re-read) much of it yet.

The detail that led us to the correct result was that a human who collaborated with the aliens was called a "Shangsyc". We got the right spelling eventually.

Judging from the blurb and excerpt we found online, the aliens were called the Shangs and came from the world of Alishang.

Wudang's comment to yulerule's answer, saying that the nickname for the police might be "Wasps", is proved right very early in the book. I have not yet read far enough to confirm it, but his comment about the story involving someone in a spaceboat of some kind having a childhood memory of seeing the Earth fleet flash by seems to ring a bell.

I was mistaken in thinking the author American; though the story starts off in New York, Ken Bulmer was British. My recollection of the cover may also have been wrong. Neither the Ace Double cover from the US shown here nor this cover of an edition by British pulp publisher Digit much resemble my vague memories.

Answer 2

I think this isn't what you're looking for, but Childhood's End by Arthur C. Clarke has the alien invasion forbidding technological progress part.