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My favorite Ulm infantry is also the morningstar+shield, although I use the pikemen extensively also. Pikemen are good for when you are facing enemy cavalry, because they break up cavalry charges fairly well with their long weapons (most knights will make their morale roll vs repel, but not all of them). Against other infantry, having a bunch of pikemen in front will stall the troops while your cavalry or archers kill them. And pikemen remain interesting into the late game against summoned troops without 30/50 morale, as always some of them will fail to attack. This series of small advantages makes them worth having as a part of your army.

The Ulm knights are great, because they have exceptional protection, strat move 2, and very good morale also. Being mounted, they suffer less encumbrance for their enormous armor. Unless your enemy has designed their force to beat you, knights will often take no losses. Finally, knights are effective against many SCs, as the standard banelord+wraithsword without a heroic ability will have trouble with a bunch of knights and sappers.

Of course, vs. heavy magic Users, you don't fare so well, but them's the breaks... Watch out for lightning and fire damage especially, and things like Drain Life. Ulms have extra HPs compared to normal humans, but compared to what else is out there, they don't have that many.