Where your army could have been gone:

1. Probably, you have been attacked and your army was defeated. Check your Military Messages.
Remember that letters can be deleted after several days or after the letters limit is reached.
If you have not been in the game for a while, ask your Substitute (if you have one and if the Substitute has access to your mail) about the Military Messages.
2. Units may begin to desert due to the lack of salary. Check your Military Messages.
3. Open your Missions Window and check maybe you have troops on march.
4. Troops could have been reallocated to other domains.
5. Check Sanctuaries of all your domains.
6. Check Resurrectors of all your domains.

All answers to the FAQ