Actually, it is even easier than that.
Figure 6a on page 17 shows that when passing through
the front to the back of Spear ‘D’, Psiloi ‘C’ does not need to be aligned or lined-up with those it passes through, or even facing in the same direction, just be partially in front of them. However, once they pass through, they will be aligned and lined-up (I like to think of this like water or light passing through a grate…once through they will take on the characteristics and shape of the things they penetrate).
Note that single elements can move in any direction, even backwards or sideways, so once Psiloi ‘C’ has passed through Spear ‘D’ it has two choices; it could have it’s rear facing the rear of the spear, or have it’s front facing the rear of the spear (either way, the Psiloi
sides must be aligned with the sides of the spear, as shown by the dotted lines in figure 6a).
Passing from
rear to the front is much more restrictive; you must start directly behind and already aligned and lined-up with those to be passed through, as shown in figure 6b.
PIP Costs:-
There is no restriction on groups wishing to voluntarily pass through friends.
So a group of several Psiloi can pass through another friendly group by moving directly forwards for just 1 PIP.
But if passing through
from the back to the front, they must start already lined-up with those to be passed through.
Likewise, a group in front wishing to pass though
the front to the back of friends can also do so for 1 PIP, but groups cannot move backwards as a group, so facing will be more restrictive:-
Here the Psiloi group wants to pass through
the front to the back of the Spear group.
They cannot pass through Spear ‘1’, because they are not even partially in front of them.
So for a single PIP the Psiloi group can wheel and pass through Spears ‘2 & 3’, and will end up aligned but facing away from the spear group.
Note that although voluntary interpenetration and fleeing can pass through a friendly column, recoiling cannot, as page 9 paragraph 6 says:-
"Recoilers can pass through friends facing in exactly the same direction to a clear space
immediately behind the first element met..."
So be careful about having Psiloi in front of rear supported Warband or Pike columns.
Oh, one more thing...fleeing troops, recoilers, and elements moving back out of a Threat Zone must move in a straight line.
As they cannot change direction, they can only pass through friends if they are already aligned and lined-up with them.
(In other words, they cannot change their facing to align and line-up after having passed through, therefore they cannot pass through in the first place)
I think that covers everything.
Some potentially useful player aids can be found here, including the latest June 2017 FAQ and the Quick Reference Sheets from the Society of Ancients:-
fanaticus-dba.wikia.com/wiki/Category:Reference_sheets_and_epitomes
