Slitherine

I had a look at combat logs for some of my troops attacking enemy units entrenched on 7 and 8 and noticed that the defense bonus for the defenders was only 4, the same as if they were entrenched on 4. There was some tiny 2% increase to rugged defense chance (which didn't fire) but nothing else. Is this a bug or working as intended ?

very strange. It seems all entrenchments are halved or worse
entrenched airfield 1, gives you 0 defensive bonus
entrenched forest 2, gives you 1 defensive bonus
entrenched city 3, gives you 1 defensive bonus
entrenched anywhere on 9, gives you 4 defensive bonus

and there i was all this time thinking cities offered some defense

Actually if you could entrench a tank on 9 it gets the full defensive bonus of 9 if attacked by another tank. It only gets halved when troops are involved, so a troop can never actually entrench above 4 against another troop

So, entrenchment gives you a chance for rugged defense AND adds to your defensive value?

Thx
jonpfl

How much +defense you get depends on what units are involved.

For example if infantry is entrenched in cities or forest then the whole entrenchment level is added to it's defense.
If a Tank or Self propelled AT unit is entrenched in either city or forest then half of it's entrenchment is used as bonus to it's defense value.

Regardless, more entrechment is always better (on defense obviously).

And yes the higher the entrechment level the higher the chance of a rugged defense, but this is also dependent on other factors.

For every level of entrenchment, the defender gets a +1 defense bonus against ground and air attacks. Any attack reduces entrenchment by 1. Units with entrenchment of 2 or greater can never be forced to retreat or surrender.

When infantry attack any entrenched unit, you can see in the combat log that it says that the defense bonus to the defenders is "entrenchment/2." As far as I know, this rule only applies for infantry. Attacking pioneers do not grant an entrenchment bonus at all. In fact, I think when pioneers attack they never suffer from rugged defense.

Pioniere/Engineers bypass entrenchments enterily, so the enemies entrenchment level is never added to it's defense.

I'm actually not sure if Pioniere/Engineers cannot suffer Rugged Defense, if I remember correctly I think it's still possible (just that the chance of RD occurring is much smaller without entrenchments).