Hokay, here we go.
I'd like to first say that I play MSU ogres, and my attempts at using a fully functioning Death Star
have all failed horribly. That said, I think that every ogre army needs its hammer units, although the critical distinction between us and say the Empire is that we don't use anvil units.
Hold on there. When was the last time you held with a unit of ogres (gorgers don't count
) and then countercharged with a second? Mostly ogre units use the bait-and-switch instead: the enemy charge one unit, which flees, and a second then charges the flank. But some canny generals do not charge the obviously decoy naked bull unit and in those circumstances we need a hammer to take the fight to them. After all, one of the primary strengths of the ogre army is speed, and you should utilise that to the best of your ability. Hammer units can also be used to crack open tougher units like ironbreakers without needing to resort to a flank charge but also without falling victim to being "eggs in one basket". So what is a hammer unit?
Well, that's pretty much it. But there's more to it than that. They unit needs
a combat character in it, preferably the tyrant to be able to take on enemies head on. Thought for the Day: I would equip the tyrant with the tenderiser and issue a challenge when the unit charges: the enemy either accepts and gets slammed by overkill or they lose the attacks back that the champion could provide. Unless there's something like a Vampire Lord in the front rank, issuing a challenge is always a good idea.
So you've got the basic idea, the hammer unit is a unit of ironguts with a tyrant or bruiser. Here's mine
Fistful of Laurels
Now in any other circumstances I'd say drop the standard and champion on the ironguts, but any
extra CR at all this unit can cause is useful. You'll notice the fistful of laurels on the tyrant and wonder why I did that. It's simple, but also the crux of this post, so listen carefully: the hammer unit should be placed near lots of smaller units. It's not as conspicuous as 6-7 ironguts and tends to not attract as much firepower, and it's centrally placed to get best advantage out of the tyrant's leadership and the laurels. Also, in the event the the unit fails to break the enemy on the charge, you've now locked the enemy in place, and the smaller units can attempt to swarm around and flank.
So in summary, hammer units are for taking the fight to the enemy when flanking is not a possibility. You should attempt to charge important enemy blocks such as the general's unit: if the removal of one unit would cripple the opponent's battle line, then target that unit (but you knew that). Hammer units offer something that a lot of ogre armies lack, and that's the ability to succeed at a frontal charge. Use it wisely.