In Creating Life (The Art of World Building, #1), we looked at intelligence, wisdom, charisma, strength, constitution, agility, dexterity, and morale as traits to define for species like humans and others. While writing a description of each and how it manifests in a species is preferred, we can also assign a number from one to ten as a quick indicator of what is typical. We can do the same with the characteristics that a member of this military needs in order to be accepted or successful.
Officers will require higher mental traits, while enlisted troops, expected to do most of the fighting, need better physical ones. While deciding the latter, think about what weapons they prefer. It takes greater dexterity to use a sword or bow than a cudgel. Superior dexterity is a needed trait for skilled swordsmen, but a crushing weapon depends on strength. Knights aren’t known for their agility due to wearing heavy armor, at the least, but if we’re creating a group that wears less, perhaps agility is expected. Wearing heavier armor might require greater endurance, too.
For wisdom, are they skilled at battle plans, or do they make foolish mistakes? Can they learn from history, keeping and reading old plans? Do they have military and advanced training for officers in matters of running a large military? Officers must pass tests, which are designed partly for measuring intelligence, not just education.
Morale is highly prized but is not the same thing as courage. Rather, morale is partly the ability to maintain formation in the face of peril, instead of everyone running away. Militaries require this and do things like court-martial those who run, but a specialized group that doesn’t operate in formations might have less regard for it (and value courage instead). Morale is a hard trait to determine beforehand, however. We can still jot down a note about their reputation for it.
While working out the details, we may be unable to decide on everything. Returning to rework items is part of the process, so do what you can and move on for now.