A containment strategy is an offensive style of gameplay whereby the player aims to weaken their opponents by forcefully cutting them off from key resources such as stone and gold, inhibiting them from creating higher quality units and defenses. A successful containment strategy requires effort and concentration, but allows the player to wage a long war of attrition against their opponents and soften them up for a full scale attack.
How to use
In most games, food and wood are abundant, but gold/coin and stone are not. The latter two are usually required to build high-quality units such as heavy cavalry, elite infantry (such as Academy and unique units), Monks/Priests, siege units, and defensive structures such as towers, walls, and Castles. As a game gets going, all players will inevitably use up their close stockpiles of stone and gold and have to venture further into the map, competing for reserves with other players or resorting to trade.
A containment strategy thus aims to weaken opponents by depriving them of these key resources. To do this, a player avoids besieging an enemy town and instead focuses raids upon enemy Gold and Stone Mine sites, killing working Villagers and aiming to hold these sites against the enemy. This also may involve the targeted destruction of Trade Carts and boats . To do so, it is recommended the player builds several towers or a Castle near the captured mines and utilizes units to defend them for as long as possible, repeating the same strategy for every set of Gold and Stone Mines in the enemy's proximity.
If the player can hold on, the enemy will inevitably quickly exhaust their remaining resources in attempting to retake the sites, thus running out of gold and making it more difficult to field high quality units, instead being forced to rely on trash units. The player can then also intensify their attack and work to destroy enemy defenses, walls, and towers, which will exhaust their stone reserves accordingly. This makes the eventual attack on the enemy city much easier.
Containment strategies are a very successful approach to handling aggressive AI players whose behaviors are predictable, especially in campaign modes. In Age of Empires: Definitive Edition, the Hittite scenario Raid on Babylon has been cited for its difficulty, particularly in the fact that raiding the yellow Babylon player's base becomes practically impossible due to its overwhelming focus on spamming Priests, Heavy Catapults, and Legions, and aggressively constructing towers.
However, if the player uses a containment strategy and first aims on cutting it off from its gold and stone reserves to both the north and south on the map, building offensive towers around the resources and killing their Villagers, eventually the AI runs out of these resources and loses its ability to create excessive numbers of Priests and Catapults, allowing each wave of attack to weaken their base and eventually be defeated.
A containment strategy is also the best option in the The Rise of Rome campaign scenario The Battle of the Metaurus, wherein both Carthagian teams attack with endless waves of War Elephants and Academy units. Thus, the player must act fast and decisively to cut these players off from their resources before they are overwhelmed.