The key being that when a main base is destroyed the sector automatically loses all its defences and facilities, as well as the ability to attack from that sector. A problem with this is that the border usually consists of three sectors, not really leaving much option for where attacks are likely to come from. This partly comes from the number of sectors on the map, but also I think from the choice of only using Britain as a setting. A world or European map might have offered more possibilities. Anyway, once this border is set up the fight is for who can make the most powerful machines or destruction and get them into combat fastest.
Resource management is the key, as always, to the game.
Your machines build facilities to mine these resources in territories you control. You can only build in, and attack from, a sector where you have a communications base. Which makes these facilities a high priority, though luckily you get a few to start with. One thing I was originally concerned about was whether the game would be imbalanced in favour of the Martians. Luckily this is not the case, and the game is actually very well balanced, while still giving the impression that the Martian vehicles are much more powerful than the humans.