They are not protected and therefore can be destroyed or damaged. If you want to attack another player or an enemy on the Continent map, you use the units in your attacking army. The assignment of a defending army is unlocked by completing the Military Tactics (tech) research in the Iron Age. If you have unbound units it is a good idea to use them for defense, as you risk losing them if you use them for attack. You can select defending units from both the current attacking army and from the available units.

To assign units to defend your city, click the blue button on the left and then click on the units you want. But fear not: even if your opponent is victorious, all defenders will be healed and revived to full strength immediately after any battle. Fellow players have to defeat them when they attack you. The units in your defending army defend your city. You should always try to put as many troops as possible into an army. In each of your armies, up to eight units can fight. Here you can manage your units and assign them to both your attacking army and your defending army. For later ages, keep in mind that artillery units can not hit flying units. If most of the units are light units, Artillery units should not be used. A good strategy is to target all of the attack from the artillery units on one other unit at a time, until they are all gone. 2-3 Artillery units should also be used when there are 0-1 heavy units and 1-4 total artillery, ranged, or fast units. The artillery units can take out all of the heavy units, making it extremely easy for all your other troops to win the battle. If the enemy has 1-3 heavy units, using 3-4 artillery units of the previous age (Or better the same age) is very helpful. They should be used depending on the enemy troops. Artillery units can be very useful when used in numbers.

Forge of empires increase army size