Troops are essential in Alliance Wars, not because they are almighty or expensive or strong, but simply because they are necessary to capture mines from your opponent. They are also the only way you can ensure the defense of your mines against enemy attack. I will describe Ground Combat in three sections. The first section will explain how you can train your troops, the second part will deal with combat principles and the final part will tell you something about how the ground combat is decided.
How To Get Troops
In order to train troops you should first get a Training Centre in order to train your recruits into soldiers. A Training Centre alone is not enough though, because your troops also require a place to operate from. So after researching the Training Centre, you have to research the Compound before you can actually train troops. These two buildings will allow you to train poor quality troops. This is the basic ground unit, and some races will not be able to have more efficient troops than poor quality.
Several races are capable of evolving towards more efficient fighting skills. In order to do this you should spend technology in Racial Developement. After your race has evolved you will be able to upgrade your Training Centre and Compound to Advanced Training Centre, and Advanced Compound. These buildings (once they are both researched) will immediately turn all your troops into average quality troops. Only a few races have the ability to evolve even further, allowing them to research Special Ops skills. Again you will need to upgrade both the Training Centre and the Compound, and when you've done that, you will have excellent quality troops right away.
Once you have trained troops, they will defend your mines. Every 100 troops are capable to defending 1 mine (doesn't matter if its an ore mine or a uranium mine) and make sure this mine cannot be stolen. Your troops will always focus on defending the mines they are certain they can protect. So if you have 5999 troops defending all 5999 will focus on defending 59 mines, and any mines over that number could potentially be stolen by the enemy. As is obvious from what I am saying here, you can also use troops to attack. You can't attack anyone with troops alone, they will need to be flown towards the planet you want to attack. The only ship that can carry troops is the Transport vessel. Every Transport can carry up to 1000 troops. Read the fleet sections of this manual to learn more on how to send your fleet to attack. After you send your fleet, you have to wait until it arrives. The moment your fleet arrives at the battle scene, your troops will be transported to the surface. Pay attention! It is impossible to intercept these troops with fleet. Once troops arrive at a planet, they can only be confronted by defending troops. Of course the defending fleet can destroy all attacking transports, but that will only prevent the troops from returning home. If that happens, these attacking troops end up Missing in Action (MIA), but they will still fight the defending troops for as long as they were ordered to attack! Troops that are stranded on an enemy planet can still steal mines even though they can't ever return home again.
The Outcome of The Battle
Two factors decide the outcome of the ground combat. Numbers, and troop quality. Numbers will influence the outcome the most, but you shouldn't underestimate the importance of better quality troops. I will go into more detail later, right now I will describe what happens when ground combat starts. When an enemy force is attacking they need to get a foothold and organize before they can start their attack. The defender has an advantage, but they will only be able to capitalize on that advantage when they have enough firepower. In other words: if the defender has enough firepower to wipe out the attacker before they can organize, all attackers will be killed without killing a single defender! If they can't manage to wipe out the attacker before they can organize, then both sides will fire at the same time, causing equal damage (no advantage to defender or attacker). Having many more troops than your opponent will always decide ground combat in your favor. When battle is close the quality of troops will be the decisive factor. For instance: 100,000 excellent defenders will wipe out 60,000 poor attackers, while 100,000 poor defenders will probably defeat 60,000 excellent attackers, but not without suffering many, many casualties. Poor troops kill less and die quicker than average or excellent troops. Having good quality troops will save you many resources! The ground combat ends when one side has no troops left, when the attacker retreats, or when the number of ticks of combat end.