[MaxWilson]

When hostile units are in his zone of control (i.e. adjacent), and they are smaller than him, he will not attack with his weapon. He will trample them instead, as described in the manual, making a number of trample attacks which varies with the number of size classes he is larger than them. (4 size classes larger = ~5 attacks I think.) By "defensive" I think you mean "set to None or Stay Behind Troops." He will still trample troops near him, he just won't run toward them like he would on "Attack".

Trampling will not usually help lone commander against large numbers of troops, because he takes Encumbrance points of fatigue with each trample. That means he'll trample maybe 10 squares at most (2-3 turns) and then get critted by all the swarming troops, and die. The exception is a commander with either 0 Enc or low Enc and lots of reinvigoration.

-Max