A foreign diplomat is a person who represents their govenment in different countries. Also they can issue visas, and are slightly similar to a negotiator.
their aides other diplomats and leaders The voices people For the US, the State department handles that sort of thing.
When a diplomat is expelled from the country that he/she is working in, the diplomat is declared persona non grata
Yes.
they tried to board them onto trains but Hitler was sending trains to Concentration Camps to put jews to death by the gas chambers