Upkeep is Savage 2ís unique economy system that prevents long stalemates in gameplay. As long as you have a gold mine that is being harvested, your team will have met upkeep.
When upkeep is not met building armor is significantly reduced and you are vulnerable to attacks by the enemy. Conversely, when the enemy has not met upkeep, the time is right to attack their buildings.
If you are in the Commanderís seat this should always be something youíre aware of. Make sure to direct your troops on the ground to strike when the enemy fails to meet upkeep, and make sure to cover your own upkeep by protecting at least one mine.