In the beginning, this map might seem harder than it actually is, depending how you play it. The enemy/AI will attack the city from all possible sides. To make things worse, enemy units will spawn after they die.

However, your mission is not to defeat the enemy, but to hold the city for as long it is needed to get five reinforcements into the center. This will happen automatically, so you don't have to worry about their movement, apart from making sure not to block these units. And you might need to defend them of course. When they reach the center, they will switch to your side so you can use them.

There's a lot of neutral equipment (trucks, tanks and other stuff) on the map that you can make yours by letting some troops stand next to it. Doing this as quickly as possible will obviously work to your advantage.

The trick to win this map, is to lay mines on strategic places to prevent enemy tanks from reaching the city's center. Remember that enemy tanks which are stuck on mines, but still alive, will prevent spawning of these units. Using this trick can have a great impact on how the enemy attacks evolve throughout this mission.

Also, don't forget to use your artillery (at the western castle) to its full capacity and watch your back in the south!