Sizing for a quest

For the next session I am planning on having my PC try to escape an enemy camp. I was going for the size of a small army, but I am trying to figure out in medieval times what would have qualified for a small army. The group is a secret order akin to the Magi from the Mummy movie. Any and all help would be awesome.

Try building out a 100-man unit the PCs will interact with and describe how many more people there are going about doing their assigned things. The PCs will never interact directly with these other NPCs, so no need for stats.

The 100 men would be:
- lots of ill-equipped peasant foot soldiers (handle as swarms). These are the guys who show up when the Lord yells "Seize that scoundrel!" and points at the PCs
- 6, 8, or 10 sergeants with decent equipment and decent individual stats. Each leads a swarm of infantry. May / may not be on a mount
- one Lord with the best equipment and decent stats. He is on a mount. He also has the flashy visible magic equipment
- one tough guy (lieutenant or enforcer) with the best stats and almost top-line equipment. This guy has non-flashy magic equipment to boost himself.

I like that idea, I forgot to mention I was thinking of doing this as a night adventure, would you recommend doing a percentile dice to see if they were detected?