[von_Schmidt]

And on mercenary rebid: if you rebid for mercs you have already hired (or for new ones for that matter)and the province you have selected at that point gets taken from you the next turn, your bid will not go through.

Your mercs will leave you, despite being nowhere near the province in question and your bid being the highest.

Basically, make sure you have selected a province which will remain safe; your home province is a good choice, unless an enemy is near (or a random event takes it away from you - always fun).