By now you've probably heard the term "farm" already. If not, please refer to Raiding Sectors.
Most commanders, when they think about farms, will envision raiding for convoys full of resources. However, there are commanders out there who want something more than your resources. They want blood. Blood is a tempting mistress to commanders who want to show a high level of dominance. Only those commanders who crave dead enemies more than resources will achieve the highest levels of battle experience.
Now, where does a commander go to kill? Some hit other sectors with only rarely getting a victory worth mentioning. Others hit deposits where they will see an increase in defensive troops to slaughter (and, if they're lucky, alot of offensive troops caught with their trousers down). But the best sources of locations, by far, are emitters.
Emitters house massive amounts of units defending or offense getting upgraded with mutagen. Smaller, non-upgraded emitters usually house lesser amounts of units. The largest of emitters can withstand the largest of attack forces, decimating their numbers on both sides in massively glorious (and messy) battles. All defending commanders will see battle experience from these battles, split up according to how many units each commander commited to defense. But the attacking commander will see so much battle experience, even at the loss of massive amounts of troops, that he could attain a whole new level of understanding and battle enlightenment.
Getting over 4000 experience is actually common when attacking emitters. Some have even gotten over 15,000 in just one battle! The only thing stopping many commanders from do this is the amount of troops they project in losing from such battles. Only those commanders who have attained the highest levels seen can understand that without sacrifice, there is no true domination.
Infestations and Experience
Those commanders who have taken it upon themselves to do their part in ridding this world of the mutant vermin will tell you that the rewards do not necessarily always reflect the costs associated with this war. But all commanders can agree that experience is there.
The higher and more difficult the infestation you raid or the site you defend, the more experience you'll get. I personally know how much you can expect at each level, soldier. And it is costly....very costly indeed. But the experience you get from the highest levels of the infestations or defended sites rivals that which you can get from even the most heavily defended emitters.
Millions of mutants have fallen from this commander's relentless fighting, both in attacking and defending. And I can tell you, I've learned alot. Commanders, it is worth it. I went from level 64 to level 71 in the time it took us to save those damned engineers. It has paid off not only in the research and technology they can bring. But, it also made me a much wiser commander. And that, in my opinion, is worth far more than the soldiers who fell serving the effort.