Fate of diplomats & others at war's start

What becomes of diplomats and other citizens of nations that find themselves at war with one another?
For example, when the U.S. found themselves at war with Germany, Italy and Japan, did these nations round-up all U.S. diplomats and other citizens. What happened to them once they were in custody?

Enemy aliens can be interned for the duration of the war. However, you can’t intern people with diplomatic immunity: you just tell them to leave the country.

In declared wars, they’re declared persona non grata and given a deadline to leave the country. After that, they are interned, but it’s usually enough to get everyone out.

This, of course, assumes that the country is “playing by the rules.”

I’ve been led to understand that egregious violations of diplomatic immunity are quite rare (e.g., detaining or even killing embassy staff), but I really don’t know. Can anyone point to any examples, if there have been any?

The most famous was the semi-governmental siezure of the US Embassy in Tehran after the Iranian Revolution.

That popped into my head right after I posted - my memory was a little foggy on just how government-sanctioned the whole affair was. Thanks.

Enemy aliens and diplomats are generally interned by the host country. Diplomats are of course agents of a (now) hostile government and the aliens are presumed loyal to their native land. Treatment varied. I think efforts are/were generally made to exchange diplomats certainly and civilians as was possible.

In WWII we exchanged interned diplomatic staff with the Japanese at least (in late '42 IIRC). (The quickest link I could find on this was a book review touching on the subject http://stonebooks.com/archives/980225.shtml ). And of course the internment of Japanese aliens was extended to significant numbers of Japanese Americans.

Here’s something on the internment of Italians in the US in WWII http://scottoline.com/internment.html

And on the Germans in the US and Latin America in WWII
http://www.foitimes.com/internment/