Mercenary Recruitment Question:

[Saxon]

I doubt I am the oldest regisitered, but I have been around a long time and own all three Dominions. Still, I get no respect...

I have gambled on merc in a contested province many times and lost more than a few. Still, it is usually worth it, as you really need those troops in that spot. Against the AI, you are likely to face a second attack right away, so even if you held the province, they will be coming again...

[Nick_K]

Movement of units into friendly provinces happens before combat though. If I'm facing a big AI attack and want to recruit mercs, I won't recruit them in a province I might lose. Instead, I recruit them in a safe adjacent one then move them into the contested province next turn. That way I also get them to hold off further AI expansion if I lose.
Of course, if you want to attack with the mercs, recruiting on the borders is best.