To start conquering cities, you need to build up your army to a size that is equal to or greater than the city's population. Once your army is strong enough, you can launch an attack on the city.

Defending your cities requires a mix of strategic placement of defensive structures and keeping a portion of your army stationed in each city. Always be ready to counterattack any enemy invasions swiftly.

Yes, you can upgrade your army units to make them stronger and more effective in battles. Upgrades can be purchased using resources you gather from conquered cities.

There is no specific limit to the number of cities you can conquer. The challenge increases as you take over more cities, requiring better strategies and resource management.

If you fail to defend a city, it may be invaded by enemies who will then control it. You can try to retake the city later, but it will be more challenging due to the presence of enemy forces.

Yes, different terrains can influence combat outcomes. Some terrains may offer advantages or disadvantages to certain types of units, so consider this when planning your attacks and defenses.

Alliances with other players are not directly mentioned in the game description. However, cooperation could be simulated through coordinated attacks or defense plans if the game supports multiplayer features.

Population is crucial as it determines the strength required to conquer a city. The higher the population, the larger your army needs to be to successfully take over the city.