First you choose one out of four different characters to represent you, Scarlet (red army), Oberon (yellow army), Caesar (green army), or Madcap (blue army). The game is split into 10 levels - the first 9 are groups of 3 territories which can be completed in any order, while the final 'Mother of All Battles' has its own surprises.
Land is mostly of sand, grass or ice. You start with 100 men and you can use whatever quantity you find necessary on each island. The rest men left will go to another level with another new 100. In the second half of the game you can freeze men to save them for the Mother of All Battles. Once you select your island and place for your HQ, you must do some research for better weapons and defences. On the roof of your buildings you can put protectors like archers, gunmen, boiling oil men, and later on even laser turrets. If you send a team of unarmed men into an unoccupied square, they will build an additional base there, with larger armies completing this more quickly.
Later on higher levels, you'll also build mines and factories, as you'll need to dig a certain material for higher level weapons, depending on whether the area you're on is rich with a certain material or not. With each next level, you'll start from a higher technology level and be able to progress to one higher level up than at the previous level.
If there is more then just one enemy, you can make an alliance until you crush the other one - three of you can form an alliance against fourth enemy. For what its worth, a certain numeric level of defence is always stronger from the same level of attacker, and men that are not armed (conscripts) can only kill enemy soldiers, not destroy or attack enemy fort.
The main thing as always in strategy games is to be the sole survivor and lead your men to victory, experimenting on vicious technologies, equipping your men, making perfect soldiers out of them, produce shields, weapons, planes... to dominate the world and crush your opponents.
You can do the battling only in a certain quadrant, but don't be long as your men will automatically start building the fort, and it will be at the bottom of age level and you'll need to invent everything for that one again.