Combat rating is the system in wurm, which decides how often you miss and get missed in combat. It is a numerical value calculated from a variety of factors. A higher combat rating makes you hit your opponent more, while making your opponent hit you less.
When two players do battle, combat rating is used to decide how large a percentage chance each player has to hit their opponent.
Combat rating is a value derived from many variables. It can be affected by the environment.
Combat Rating system info from Rolf:
First of all, the bonus is applied to something that is called Combat Rating or CR for short in the system. Every creature has one. It is very similar to the concept of levels in other games, just that it fluctuates a lot more in wurm. It is the basis for calculating the chance to hit another creature. Players have a base combat rating of 4.
If the troll I am fighting has CR 10 and I have CR 4 I have about 4/(10+4) chance to hit the troll, or 29% every attack. The troll on the other hand has 10/14 so it'll hit me 71% of his attacks. Very simplified. There are parry bonuses and covers involved in that specific algorithm. Also your basic fighting skill is added 1 per 10 in skill, so if you have fighting 59 you have a CR of 4+5.9=9.9 in base CR. Monsters have their type modifying base CR, making Champion creatures have maybe double the figure of the standard type.
A lot of things also affect the combat rating before that algorithm. Things such as footing, if you are prone, certain combat moves affect it negatively, being flanked, height distance to target, focusing, being drunk.. things like that. And also the kingdom bonus.
Now, in Player versus Player combat the base fighting skill is added 1 point per 5 in skill instead, so a player with 99 fighting skill would have like 23.98 in base CR and one with 50 fighting skill would have CR 14.
So how much is the kingdom bonus? The kingdom bonus is 2 if your kingdom has less than 10% of the server population. It is 1 if the kingdom has 20% or less of the population.
Acquiring combat rating
Every player in wurm and every creature has assigned a specific combat rating at all times. However, it is a large bundle of variables, not only determined by your skill, but also by your location and your kingdom population.
Confirmed variables to effect your combat rating:
Fighting skill. One of the basic ways of acquiring a high combat rating is, of course, to get a high fighting skill. Your fighting skill gives different combat rating depending on whether you are fighting an NPC creature, or you're fighting in PvP combat.
Normal fighting (fighting subskill). "Max combat rating bonus for normal fighting was raised to 2.5" -Release notes July 12, 2011
Kingdom bonus. An Elevation- and Chaos-only feature, there are two steps to this kingdom bonus. If your kingdom has less than 20% of the server online, you receive an extra 1 combat rating. If your kingdom constitutes less than 10% of the server population, you gain another point of combat rating, for a total of 2 extra.
Suspected variables to effect your combat rating: