ORIGINAL: springel
I did experiment. I gave one battalion a defend order, formation 'in situ' and facing East. Then I ran the game for a few minutes, looking at their activities. Nobody showed any other activity than being in position, but all the facing blocks jumped into the right direction. And all units showed still being entrenched.
I have just become in the mood for Command Ops, through all the talking about the patch, and the beautiful work of Daz, so although I played a bit around with CMRT, I preferred spending a night with the Veve scenario. Where I was unpleasantly outflanked by the German AI and had to describe it as a disaster, just a short while after I was so satisfied with the fighting at the pass.... [X(]
Since you like to micromanage, a defend "in situ" is most effective if the units are individually assigned appropriate over watch / defensive spots for the terrain, and then reattached to the higher HQ with a defend "in situ" command after reaching those spots.
I'm playing the All American over Nijmegen scenario, where the Nazis can attack the 508th Reg's flank along the Kranenberg-Nijmegen Highway via the bridges over the waterways paralleling the highway.
I assigned individual companies to secure critical crossings along the highway line, moved the BN HQ and remaining companies / mortar platoon to a central position amidst the secured crossings as a tactical reserve, reattached all to the companies to the HQ, and then issued a defend "in situ" order to the BN HQ.
It blocked any incursion on the move to Nijmegen center and the bridges by the remaining 508th Reg units and allowed freer movement of the remaining 82d regiments toward critical crossings for the XXXth Corps units arriving at a later time.
Basically, individual units are assigned defensive positions at mobility chokepoints and then ordered to defend "in situ" at those spots until AI enemy counter action dictates a change in tactics.