Reinforcements to Allies and Friends
Sending troops back and forth just to get forts- this can be solved with a cool-down time at both ends of the trade
Giving troops to help new players suddenly become like mighty gods- this can be solved by having the troops disappear or return to the original player after a set time
Sending hordes of troops to help people farm- this can be solved by only giving this option if you are under attack and after the war the troops return to the original owner