Alliances - how do forces support each other

How alliances work in terms of supporting forces is very difficult to
do by trial and error, but I wonder if anyone knows the answers to
these questions;

1. Will an ally's ships, forts and arty, support an attack even if
they are not hostile with country being attacked.

2. Will allied land units on reserve mission react to repel invasion
of an allies sectors. Eg if Red and Blue are allies and Blue is
attacked, will a Red unit on reserve mission in range, move to the Blue
sector and defend? What about if the Red unit is based on the Blue
sector and that or another Blue sector is attacked? How will the unit
react in these cases? And need both allies be hostile with the
attacking country in order for this to work?

3. If an enemy submarine fires a torpedo at a Red ship, will a Blue
destroyer in range return fire?


Can anyone think of any other scenarios worth mentioning?

>
> > 3. If an enemy submarine fires a torpedo at a Red ship, will a Blue
> > destroyer in range return fire?
>
> No. Feels wrong to me.

So an ally cant supply a dd to help defend ships against sub attack?
Sounds a bit strange.

In these scenarios what is the difference between "at war status" and
"hostile" are they essentially the same. Info is very vague about
this. Do these states affect how allies support each other?