When do enemy armies get an extra turn?

In the PC version of Romance of the Three Kingdoms XI, all enemy factions/armies get an entire extra turn at some point. This happens perhaps once per scenario/game. Enemy units can be observed to move and attack twice.

Why does this happen?

Can it be predicted?

Can it be avoided?

Solution 1:

The double move is just due to the ordering of turns. If you take your turn before the enemy, then they take their turn the next month before you, it will seem like they just got a double turn. But everyone still moves just one turn per month.

Solution 2:

AI does not get extra turn in ROTK XI, ever. What you observed is an enemy unit movement followed by normal attack + another normal attack triggered by "Chain Attack" skill of the enemy officer. Now, this double attack per turn does not trigger every time, but rather has about 50% chance to occur.

Also, some officers will assist other officers after they have already moved for that turn, which may seem like they are attacking twice, and even trice per turn. Once again, both player and AI get to do stuff once per turn no matter what.