I was thinking today, and I must say soemthing about the humans vs yeerks. I was thinking about what would have happened if the humans had gone to war agaisnt the yeerks, openly, with no Andalites coming for sometime. I believe the yeerks would regret the war completely. The initial battles would be won by Yeerks, due to advanced technology, bug fighters and such, but they have several problem
1. The yeerk force is only a task force, not a invasion force. They only have about probably twenty-thirty thousand HB and human controllers, tops. The taxxons would be little threat, as they are easily dispatched as would the gedds.
2. Firepower. From what I've seen in the books, yeerk ground forces would be woafully underarmed, as all they seem to have is mainly hand held dracon beams, not ideal for open combat. They have some heavier weapons as well, the Venbers dracon assault cannons and the 'lincoln memorial on a swivel mount' Tobias saw. They seem to have no room clearing weapons liek grenades, though Aldrea in the HB chronicles does mention something like quantum explosives or something like that. Us humans on the other hand, have more guns that the entire bloody yeerk empire! We have long range weapon and sniper capable of popping HB melons (heads) at a kilometer away! We have grenades, mortars, tanks and such. While tanks could be stopped with a well placed dracon blast, one abrams cannon round could tear twenty HBs to shreds, and a taxxon assault force of two hundred could be decimated entirely by a marine squad with M-16s and a fifty calibre machine gun.
3. Air support. While bug fighters have shields and dracon beams and such, they are not made for atmosphere. Our fighters can do mach 4 and over in atmosphere, and have formidable armnanents. Missiles can be shot down, but sidewidners at close range would be impossible to catch in time. Since yeerk fighters operate on line of sight in air-to-air combat, we could definately level the field with thirty mm vulcan chain guns and such. While the bugs have shields, they couldn't take 30 mm super dense depleted uranium rounds in they would quickly wear down and then the fighter would be torn to bits. Other than bugs, the yeerks have no real gunships or anything, except for a mention of 'skimmers' in book 18 which I presume are their version of tanks, or mobile artillery. We have apache longbow gunships which could easily turn a yeerk force into paste with their flying arsenal. And, the estimated number of fighters the yeerks have is maybe one hundred, probably lower. We have thousands so we would win through sheer quanity anyway. As for the bladeship, it could cause huge damage, but could be destroyed by a couple dozen SAMs (Surface to Air Missiles)
All these things aside, think of it. Earth would turn int oa hellhole one hundred tiems worse than the HB homeworld ever was or could have been. Think, one thousand andalites and 700 HB warriors caused the yeerks so much greif and destruction. Us, with milions of soldiers, and the fact we are brutal and crazy in battle, would turn earth into ta meat grinder for yeerks. Also, about 20% of humanity would call the yeerks demons and go on a hoyl war against them. Think, the yeerks would have to engage in things like urban and jungle warfare, the most brutal types of war imaginable. building to building, house to house. It would be such a slaughter for them that instead of strengthening them, they would send in dozens of ships to earth and weaken their front everywhere else, allowing an Andalite breakthrough.
So in fact earth may have become their undoing.
Not to say we would suffer too though, millions of civilians would die. This would terrify some to submission, others to revenge, or others to hiding. So Earth vs Yeerks in full scale open warfare would turn earth into a slaughter hosue for yeerks everywhere.