Warlock – “Cultist” [Campaign 4, Mission 3]

does anyone know how many blue Castles are there?
because I'm capturing the third Castle and can't make it to the attack from the other side by the end of the week, armies are zero

I've attached a map and marked with numbers the order of capturing Castles that I used. Played on Veteran difficulty
Demons btw. always (at least in my case) go through the second Castle; I intercepted them for the first time with my main hero, then due to the fact that the number of Castles was large and I didn't take units from the first two, the second hero had an impressive army and, although with difficulty, fended off the red aggressors.
Also, you must always remember two things:
1) Do not delay capturing Castles. The best option is a blitzkrieg at the beginning when the enemy hasn't strengthened yet; the defense of 3 or 4 Castles was not very strong (to put it mildly) when I captured them
2) Intercept enemy heroes. For example, as soon as I noticed an enemy hero (blue), I immediately rushed into pursuit of him.