I believe if you use too many mortars close to hq they’ll discover it
Not sure about the other ways

- If you have your FIA commander out in the open then a passing patrol or aerial unit can spot your commander and in doing so, your base. So keep away from main roadways and enemy air bases. I would personally recommend using a building to house your commander.

- Mortars positioned at or near your base (as mentioned in a previous comment)

- Failing ANY traitor assassination mission (they give the enemy your HQ location)

- When you lose an asset (resource, outpost etc.) the enemy has a chance of finding intel. (not 100% sure on this one but it happens to me)

I cant think of any more ways but I'm sure there are some.

Originally posted by Marshmallowsam:

- If you have your FIA commander out in the open then a passing patrol or aerial unit can spot your commander and in doing so, your base. So keep away from main roadways and enemy air bases. I would personally recommend using a building to house your commander.

- Mortars positioned at or near your base (as mentioned in a previous comment)

- Failing ANY traitor assassination mission (they give the enemy your HQ location)

- When you lose an asset (resource, outpost etc.) the enemy has a chance of finding intel. (not 100% sure on this one but it happens to me)

I cant think of any more ways but I'm sure there are some.

I think those four are the key triggers. Havent encountered others.