This excerpt is from page 10 of the Warhammer Annual 2002 in the section titled, "RUN FER IT LADZ!"
The Warhammer rules say that when a unit breaks, fails a Panic test or flees for some other reason, it moves directly away from what caused the unit to flee. Usually this is quite straightforward - if a unit is splatted by a Rock Lobber and panics, they flee from the Rock Lobber. If a friendly unit breaks to the unit's left, the fleeing unit moves to its right. However, things are not always this simple. For example, what if a unit is fighting in close combat and then charged in the rear? In this case it must flee through an enemy unit if it were to flee directly away from the source of panic. The same can happen if a unit fails a Break test, whilst fighting units on opposite sides.
So, how do you resolve this? Well, I have a short list of priorities which I go through. The order is:
Move as directly as possible away from the cause.
Do not move through an enemy unit.
Do not move within 4" of an enemy unit.
Do not move through a friendly unit.
If at all possible, a unit that flees will attempt to fulfill all four priorities. If this is not possible then it will ignore these priorities in ascending order. For instance, if a unit cannot move directly away from the cause and stay more than 4" from the enemy without going through friends, then it will go through friends as this is the lowest priority. If a unit cannot physically move directly away from the enemy without going within 4" of an enemy unit, then it will do so if it has no Other option. Again, this is because moving outside 4" is a lesser priority than moving directly away.
Now, this is where a degree of common sense is required. Which route takes the unit as directly as possible away from the cause? Obviously a straight line is the most direct, but this is not always applicable on the field of battle. So, the route must be as close to this imaginary straight line as you can get it, whilst fulfilling the other priorities. This is best demonstrated by diagrams 1 and 2, shown below.
This is where things can get a bit tricky - when can the unit approach within 4" of the enemy and when can it not? There's no hard and fast rule to apply here, unfortunately. To decide, I usually follow the guide that if none of the flee movement would take the unit further along that imaginary straight line, then they will approach within 4". Diagrams 3 and 4 below show what I mean.
