Ok, this seems to be an ongoing question and we have gotten multiple answers. When you check deploy leader on the sanctuary, does that mean your leader and his brigade is safe or does that mean they will be deployed in the event of an attack?
Sanctuary description clearly explains everything
"Send your troops and leader into the sanctuary to protect them from attacks. When your castle is attacked, troops in the sanctuary cannot be attacked"
Once you check the leader and send troops to sanctuary and click "protect", your leader and troops are safe for the duration of time you chose (max 12hours). Your leader and troops wont get out of sanctuary, if you get attacked.