Penetration/Protection

[pgr]

I was thinking about going some unit modding, and as I looked in the files for artillery and Ironclads, I realized I didn't quite know the interplay of the penetration vs protection stats. From the old wiki, the combat section has a brief mention of protection: "PM = Protection Modifier: (1-level of enemies entrenchment/10)*(1-terrain protection/10)*(1-unit protection/10)"

Is it safe to assume that the penetration stat acts as a positive modifier, such as (1+unit penetration value/10)? Does that mean in land combat, that guns with a higher penetration value can help an attacker counteract entrenchments?