In strategic conquest gamess, the goal is to overcome an enemy stronghold. In general, all enemies are gathered in one (or more) point (s) so that you will have to attack these spots precisely.
To do this, manage your troops and send them into battle. Start to conquer the neutral zones in order to rally them to your side. You can then launch an assault on strong enemies to eliminate them permanently.
Most of the times these games will be Conquest Tower games (opposed to Tower Defense games), and they have increasing levels of difficulty.