... and other orcish motivations.
This post has been sitting in my draft pile for a while, fortunately Erny's Orctober has finally got me to knock it into a finished state, and so improve my pathetically slow posting rate.
Warhammer orcs aren't complex / confused like World of Warcraft orcs - they're evil, violent and none to bright. They're also a popular army choice, which means coming up with scenarios for them. And to me that means giving them a range of motivations that fit with their character, which I like to feel is a bit more three dimensional than that portrayed in the rulebook.
The shaman did it - as illustrated by Warlord Paul and Thantsants, the shaman, as the intellectual of the tribe, can help out when a scenario is more quest-like than war-like. And given their tendency to the spiritual or downright possessed, it can be as deranged a quest as you'd like! I see the relationship between an orc warlord and their shaman (or a shaman and their pupil for that matter) as something like that portrayed by David Gemmell with the Nadir, except an orc shaman is far more tribal and has no interest in uniting the fractured orc tribes.
The goblin / half-orc did it - half orcs are noticably brighter, and goblins are considered more cunning, than your average orc, so these provide extra possibilities when a scenario requires brains as well as brawn. However unlike with the shaman your thinkers here are down-trodden and despised, which gives the scenario a bit of a twist.
Uneasy lies the head that wears a crown, or, the warlord did it - your orcish warlord probably got to his position by killing and eating the previous incumbent, and will probably pass on the crown in the same way. He also won't be the first despot to realise that uniting against a common foe is a good way to keep the tribe in line (as long as the battles go well, that is), and might also have the advantage of cutting short the careers of potential contenders. I like to see these sort of campaigns as petty raids and feuds rather than the grand battles that seem to be depicted in modern Warhammer, but each to their own.
The freebooter did it - personally I think Orks are a bad fit to the 40K background, but the freebooter mindset does seem a good fit to orcs of any era. Orcs love to fight and loot, and there's clearly some sort of commerce between orcs and other races by some means or other. So I like to feel that Hector Barbossa wouldn't change a great deal if given green skin and tusks.
I'd rather be in the Dark Lands - orcish society is in a state of continual fighting and flux, so it's entirely likely that your orc invasion isn't really an invasion at all, it's just that the invading tribe is being driven out of their stamping grounds by an even bigger, tougher tribe. They just want to be left to live in peace, honest!
The dwarves / humans did it - for some reason the orc side of the table is generally portrayed as the aggressor in your typical scenario, which is clearly indicative of some sort of bias... Perhaps those nasty, aggressive dwarves / humans are mounting a punitive expedition against a peaceable orc tribe, for reasons no right-thinking orc can understand, or perhaps they're after something that's in orcish territory. Time to work out what orc buildings look like, to go along with your Warhammer Townscape.