Getting pwned by spoiler race GUs

[Llamageddon (OP)]

I think they are a spoiler race, so I thought I'd post it here. Units are listed as Centurions, Decurion AA Mechs and Praetorian Combat Mechs. They appeared on a planet with some ruins. I didn't expect this to work at all, but it is far worse than I expected.

I saw they were what looked like a lot of armoured vehicles, am guessing centurions might be heavy infantry. I made an invasion froce with about 25% more units than them, mostly made up of "tank destroyers" - medium vehicles with medium armour and two medium anti-vehicle components, and some with anti-infantry capability, plus an HQ that can cover the unit capacity. They land on the world and when they hit they seem to penetrate and destroy a unit about 75% of the time not terrible.

The problem is my units are hitting a target only about 1 in 20-40 shots. First round of combat I destroy a handful of their units, next round of combat they utterly destroy all my forces with a 100% hit and kill rate. I am just wondering what is happening here. Is it just down to them being fortified or them having much higher tech weapons or something completely different? I can't see any stats on chance to hit with my components or forces.

I know most people have been talking about using invasion forces of a minimum of twice the tonnage of what they are assaulting, so I wasn't expecting a victory of any kind; I was just testing things out of curiosity. It doesn't seem like 5x the tonnage would even come close to winning this fight.

P.S. This is my first proper invasion, so I'm sure I've missed a few obvious things from an invasion check-list anyway.

P.P.S. Didn't know if it was necessary in the spoiler forum, but I've added some spoiler tags just in case people don't realise they are in this forum when reading this post.

[TheTalkingMeowth]

Ground combat accuracy is really, really, terrible. Especially against fortified units, which the spoiler race forces you are describing are. It's even worse if it's a jungle or mountain world. You also get penalties if the planet is not habitable for your species (temperature or gravity issues).

It is a bit odd that they had 100% hit rate. The kill rate being high is expected; they have fairly high tech, so their weapons do lots of damage and have high penetration.

[Llamageddon (OP)]

That might explain most of it then. The planet has no atmosphere. Although there doesn't seem to be any tech I can reasearch that would help with that.

[TheTalkingMeowth]

You can research extreme pressure, temperature, and high and low-g capabilities and add them to your units. Units with a relevant capability get double chance to hit.

I'm not positive, but I THINK the extreme pressure one only applies to too-high pressure, not lack of atmosphere (which I think doesn't impose a penalty. The ground combat terrain rules are scattered about the changes thread).

[Llamageddon (OP)]

I'll have a look at the changes, if no atmosphere and no terrain type doesn't cause any penalties then my troops really are unbeleivably awful, or I am missing something more obvious.

[Tavik Toth]

It should say what terrain type the body has in the system information view. 

Edit: Unless it's Barren which as far as I can see is the only time it doesn't say the terrain.

[Llamageddon (OP)]

Tarrain "-". I don't think bodies with no atmosphere can have a terrain type. Body "type" is "Planet - Terrestrial", temp is 45c, gravity 0.50. Only thing I think I can research that might help is Extreme Temperature Capability.

[Demonius]

At low tech level, bleed them dry until they run out of resupply just as you do - then its a few months of trading 1-2 units per attack vs 1-2kills. You supposedly have more reserves to bring there. 25% more is just not cutting it against a dug in superiour foe. The fallen will not be forgotten.