Were people or at least governments in the UK / US awware at least of the widespread persecution of jews in nazi germany?
/u/PeculiarLeah has previously explained how the Allies knew about Dachau.
/u/commiespaceinvader has previously talked about Eisenhower's efforts to preserve records of the Holocaust and another thread about the liberation of Dachau.
I also refer you to my previous answers regarding How did different Allied armies treat people liberated from concentration camps? and Did people in the West know about the Holocaust while it was happening?
/u/estherke
This is a very popular question genre.