Battle rules question: Intensity

[Balin]

Specifically, how does one set the Intensity for a Battle? Does it change during the Battle? The Core Rulebook has no Battle rules, so I'm going by those laid out in the Starter Set. But as far as how to set the Intensity score, the only guidance Appendix B gives is to paraphrase, the larger the battle, the higher the Intensity score. So would for Small/Medium/Large battles, would 5/10/15 be appropriate, or is that too much?

First time Pendragon GM here, so any guidance is welcome.

Edited September 16 by Balin

[Morien]

Basically the intensity governs how much control the PKs have over their own fates. A common House-rule is to make it an opposed intensity vs the unit leader's Battle, in which case you should use something like +5 to your suggested numbers. 

And you definitely can modify intensity during the battle too. A surge of friendlies/enemies can easily modify intensity by -5/+5, for example. It also makes the battle feel more dynamic. An ambush by the enemy army might have a high intensity to start with despite being a smaller army, etc.