This is what i come up with so far.

So, there are two special terrain types not used in a regular game see
terrain.txt, reuse bottom one for a new terrain type,call it low hills
with same stats as normal hills,possibly lower movement rate,change its
combat modifier to a negative.Easy i thought,and tested out some sample
combat,matched some units up from a number of different terrain types.

The battle screen its reporting +-100%, but the actual combats are not
coming out as you would excpect them to.Any thoughts??

As a bonus if you use special 2 for your terrain you get to fight
a coastal battle screen.

Its not to do with the reuse of the terrain tiles as i have been using
them for some time with no problems in regular combat were all bonuses
were positive.

Here is the data, all units were 30Attack 20 defence sat adjacent prior
to combat.7 units vs 7 units.Mountain have only 3 combats as their very
one sided and dont need to big a sample.

Attcking fromGrass to defending on AmbushTerrain +-100%
Attacker has 1,2,3,5,1,2 units left after 6 combats

Attcking fromAmbushTerrain to defending on AmbushTerrain +-100%
Attacker has 5,1,2 defender has 3,4,2

Attcking fromAmbushTerrain to defending on Grass 0%
Attacker has 4,4,1 defender has 1,3,2

Attcking fromMountain to defending on Grass 0%
Attacker has 7,6,7 (very healthy)

Attcking fromGrass to defending MonMountain +100%
defender has 7,7,7 (very healthy)

Attcking fromMountain to defending fromMountain +100%
Attacker has 2,3 units left defender has 2,2,2,1, units left

Basically, he thinks that the combat structure is different from the past - each battle is a series of attacks where the units switch back and forth from attacker to defender.

Terrain now plays a factor for both attackers and defenders.

Still, traditionally, terrain favors the defender.

Ambushes should be handled (in a perfect world) with a chance that the defenders (and maybe, the attackers - base it off randomness and the vetran status) get a number of free attacks.

It would certainly give small units a chance to wipe out larger armys. And it was all Hannibal had going for him.