Defending with Stealth Units

[Immaculate]

Lets say i have a province with PD and a few units hidden in it (for whatever reason) using the scout-like ability to stealth.

Now lets say the enemy invades that province. will my stealthed units keep hiding and start the next turn in an enemy province (assuming our PD lost the battle) or will they help defend the province alongside our PD? if they defend, do they go back to hiding after they fought?

Thanks.

i.