while reading about rocket science and interstella colonisation (KSP player here
) I realised something interesting about x-com... namely the problem many people bring up about the alien invasion.
the problem most people point out is that the aliens don't attack in force when they could easily over power us and how they never seam to develop new technologies such as armour and the likes.
what I realised is they don't because they can't. the aliens had to travel to our solar system from where ever they started. and as anyone with the basic knowledge in space travel can tell you the biggest hurdle in getting anywhere in space is delta V (changing velociety) what this boils down to is the heavier your craft the more power you need to speed up and slow down. which means that the aliens had to limit what they carried (i.e just what they needed to survive and start building for war) and when you combine this with the alien reporduction (something in the original game files that wasn't implemented into the game) which indicates that the aliens are essentially clones what this means is that a small number of aliens were on the initial ship with a bank of genetic data (or embrios) which they then had to clone to produce their army, along with elerium and manufacturing facilities to build space craft (and the alien alloys).
this would explain why during the first year before the start of the game alien activity slowly increased (they were collecting resources and building their war fleet), and as so much of their industry is set on producing weapons and ships as well as cloning soldiers to replace those destroyed/killed by x-com they don't have the resources to dedicate to research. and if they use the same technology as TFTD aliens every clone is implanted with knowledge based on his job (soldiers taught how to fight, navigators how to fly ect) meaning that they have little individuality which limits their creativity, having not learned over the course of a life time but instead getting information fed directly into their brains with no questions asked. meaning they only produce the weapons and craft that they have the information to build.
compare this to x-com. x-com does not have to worry about gathering food as we have ample supply on earth, we don't have to worry about building weapons (at least not at first) as we just buy them from arms manufactures (and later we just capture them from the aliens) we don't have to worry about soldiers as we already have 7 billion people the majority of whom are of an age and are capable enough to fight if needed (in an emergency the world's armed forces could get 15million+ troops to combat the aliens) and our old fashioned style of learning where we have to learn things as we grow by asking questions this gives us the ability to ask "what if we do this instead of that"
on top of all this the fact that earth mobilised to combat the aliens (forming kiryu kai, X-inv and finally X-com) this forced the aliens to fight before they were ready (which is why you battle sectoids the weakest aliens first, followed by floaters who are of limited combat effectiveness instead of snakemen and mutons) this would also explain the terror missions, the aliens strike cities to cause disruption (draw you away from their other activites) try to turn public opinion against the war (much like the bombing campaigns of WW2) and kill off large numbers of humans to reduce our fighting power (they can clone entire armies in a short space of time, it takes us years for a baby to grow into a combat effective soldier)
this also goes to explain why alien activity increases steadly as time goes on. initially there is only a hand full of aliens with a small number of small craft to conduct missions while as time goes on more and bigger ships start showing up (those big ships take time and resources to build, it's more efficient to build ten small ships to collect resources than one big one that could be lost while on a resource harvesting mission)
it could be argued that the aliens could have mined the outer planets for resources to build their fleets to invade earth (and they probably did) but one of the key missions they conducted on earth was... harvesting missions. they were activly harvesting earth flora and fauna for food (as indicated in the alien food research) this was their one weakness and why they were forced to fight before they were ready, they didn't have the food production facilites on mars to sustain their population (that and you need bio mass to grow clones)
this all also explains the cattle mutilation. why did the aliens only take parts of the cattle and not the whole thing??? they took what they needed the parts rich in what their diet required and dumped the rest to save weight and thus fuel while traveling in space (E-115 is a finite resource limited to only what they brought with them)
these are just some of my theories about why the first alien war went the way it did
