Why cant you use your retiniu army in ck2?

In Crusader Kings II (CK2), you cannot use your retinue army in the same way as regular levies due to the game's mechanics. Retinues are professional troops that require a specific amount of military experience and are maintained through a combination of your personal holdings and resources. Unlike levies, which can be raised from vassals and territories, retinues are a permanent standing force and cannot be summoned in the same fashion as large armies; instead, they are always available for use as long as you have the necessary funds to maintain them. This distinction emphasizes strategic resource management and the unique composition of your military forces.