Most proffesional armies are centred on the ethos that a small number of well equiped and well trained troops will triumph over large numbers of ill equped and trained troops. This is largely true especially so in open warfare where use of Tanks and Air support can destroy vitually any strong point in an enemies line within minutes of it being identified. Leaving infantry to clear and then occupy and defend strategic positions leaving attacking to the tanks and motorised units to carry out "blitzkrieg" which is the foundation of modern open war.

However things get really complicated now as the enemy troops will try to draw the superior force into urban warfare to drain him of his strength and stretch his forces thin. To counter this the modern force deploys infantry specialy trained to flush out troops from buildings and a lot of many soldiers training consists of urban warfare training and house clearing as this seems to be the only real field in which the infantry man really excels. One of the things all commanders should know is never to commit tanks to urban warfare as there are plenty of places where people can hide so as to disable said tank. The ideal solution to urban warfare is to level the city but now that a military has the combined weight of the nations media and public concious on it's back it has to avoid "unnesercary civilian casualties".

However the bottom line is no matter how well trianed or numerous you're armies if the local populace does not support you, or at the least not interfere, you are doomed to failure unless you have several million bullets to spare in quelling the population or are willing to drop a nuke. Thesame happened to the French in Spain who had so many troops tied up trying to stop the guerillas that they couldn't stop wellington.

And of course remember the greatest saying of all, "An army marches on it's stomach and it's purse." Meaning if you can't keep the supplies and pay rolling in you're doomed.