Need help with large campaign

[Eltharon]

The title sort of says it.
(Long post)
I have some basics of the plot worked out, but the little details and interconnecting bits tend to give me trouble.

Note: This campaign contains as much RPing as Hacking and Slicing. My players (and me) like it that way
Note 2: Some of the characters are nobles
Note 3: This uses AGOT D20, bits of Iron Heroes, Elements of Magic, Cry Havoc, and maybe some other stuff lying around
Note 4: I may play this campaign onlinbe here, so if the first paragraph makes you long to play, just PM me, but don't read the replies or the rest of the post...

Overall metaplot: The world of Erinoth (low magic) is loosely based on George RR Martins Song of Ice and Fire, in the sense of many Noble houses vying for control of the Throne in Drakonguard. Wars erupt every so often (as in: Pretty frequently) over the title of king, land grabs, civil wars, etc. Neighboring Guishoff tries to stay neutral in these wars, though the support of their merchant houses can make or break a military camapaign. It also is a nice safe haven for defeated lords fleeing from vengeful enemies, as does the far off South, consisting of the typical pseudo-eygption state (M'eoid) and the free cities along the Great Desert (Arabic style).
Along with raiders from the Thunder Sea islands, freelanders from the Starfall Islands and the Xarroden coast (large island), and those ever strange ships that are occaionally glimpsed in the Sea of Shadows, the world is a busy place. The business is complimented by reports of goblins in the Galewyn Mountains, and sightings of stange mountain men in the frozen north. Ever so often, rumors of wizards and magic drift, as much fable as fact.
The campaign begin with a war of succession instigated by members of the Cult of the Undying, who are trying to weaken the kingdom for their attempt to summon up the dreaded demons of old, not seen for many thousands of years, in the Age of Woes and the Time of Heroes.
So. This brings us to problem one: How does to cult get a bunch of noble houses to start fighting over the Throne?

So the campaign begins right before the war. As is normal for me, I know how the campaign ends, but can't figure out how it starts. I'm really horrible at beginnings. Thats problem 2.

Which brings us to the REALLY BIG PROBLEM.
I really don't know how to take it from here to part two.

Part two is when the cult actually summons the demons and devils from Hell. Along with the support of the "true" king (as in, the king when the war started, and now obviously a Bad Guy), they come with death on their minds (and horns and bits of flame). Earlier on, a handful of elves from Q'uenlathinae (the island in the Sea of Shadows) will leave their protected home, sheltered from annoying humans, and begin to investigate what is going on. Goblins and their kin will emerge from their thousand year old hiding places towards the end (Note: Goblins live on the edge of the kingdom, so any reports of their raids are typicly laughed off as bandit raid, because what to those folk know? They're almost far enough away from the Silver Road to be savages)

Problem 5 is also annoying, as I need something for the characters to do as the demons run around blowing things up.
Now, the demons don't just appear and make headline news the next day. They move with the Kings army, after all, and only show up when needed (and then very few people come back to talk about it)

At the end, the demons and their allies will be defeated in true heroic form (with heroic music) in the heroic final battle (with the heroic arrival of reinforcements in the dramatic end of the battle (You know, right when the Good Guys are going to lose)
Sure its cliched, but hell, I always wanted to do it.

So I need to weave those semi connected connected threads into a magestic plot equal to any fantasy novel.

So, am I crazy or could this work?

Thanks
Eltharon

[Tallis]

Sounds workable to me.
Problem 1) Cult members could have whispered lies into the nobles ears, turning them against one another. Back this up with some planted evidence and forgery (and maybe a little mind effecting magic) and you've got yourself a war. Works even better if you can do it to someone that's already got the hunger for power.
Problem 2) Well if you want your players to know right away that someting is up, they could be hired to look into the bandit raids on the border (or maybe one of their relatives live there) only to find goblins.
Otherwise, a rescue mission, the cult is going to need some human sacrifices for those demons. For that matter, maybe the PCs have been captured and their first mission is to escape before the sacrifice.
A diplomatic mission to a neighboring county that was on the other side in the war, there are likely to still be some problems that need to be worked out. The diplomat could also be going to another kingdom, asking for aid to recover from the war.
Plenty of opportunity for pirates, and they're always fun.
Problem 3) Throw in bits of information in the early adventures that may not seem related at first, but then fill in the blanks when you want to make the change to part 2. Make sure it's memorable enough to allow the players to make the connection.
Problem 4) What is problem 4?
Problem 5) The players could be of dealing with pirates, or on a diplomatic mission to the desert states. They could even be following a false lead trying to track down the cult. When they get back, the war is already in progress and they have to fight their way past the demons to get to the final battle in time.
Hope some of this helps.

[Eltharon]

Problem 4 is that I can't count.

The thing with problem 3 is that I feel theres a huge chunk of plot missing, maybe even a part 1.5. Going from "war" to "demons!" seems to be missing a tidbit...

Keep in mind that any of this is subject to change if I change my mind.

Keep up the replies