Two main suggestions:
1) I think what should happen is that each army should have a modifier linked to their morale, if it gets low there is a chance that the army will defect to the closest nation you are currently at war with. meaning that you will lose some or all of the army.
2) Linked to morale, armies need to also be able to surrender. For example, if someone is attacking an army significantly more powerful the unit may surrender rather than fight (similar to the defection suggestion) where they are absorbed but with lower morale than otherwise into the attacking force. In the event of a nation that has been completely taken over by one nation outstanding naval units should automatically surrender to the attacking nation once there are no more provinces left for that nation. If the nation is taken by multiple nations then surrendering units should be divided based on the percentage of territory each nation captured (two nations each take 50% of a country, then each attacker gets 50% of the surrendered units).
1) I think what should happen is that each army should have a modifier linked to their morale, if it gets low there is a chance that the army will defect to the closest nation you are currently at war with. meaning that you will lose some or all of the army.
2) Linked to morale, armies need to also be able to surrender. For example, if someone is attacking an army significantly more powerful the unit may surrender rather than fight (similar to the defection suggestion) where they are absorbed but with lower morale than otherwise into the attacking force. In the event of a nation that has been completely taken over by one nation outstanding naval units should automatically surrender to the attacking nation once there are no more provinces left for that nation. If the nation is taken by multiple nations then surrendering units should be divided based on the percentage of territory each nation captured (two nations each take 50% of a country, then each attacker gets 50% of the surrendered units).