Questions about my plot in FR

[Telor]

My group completed the Pools of Radiance module months ago and have since joined the Harpers to take care of misc. problems that have been happening in the area. A few weeks ago, I introduced them to the Shades.
The shades enslaved a clan of dwarves in their region and the party managed to free them without drawing much attention.
They were sent back to Myth Drannor to make sure that the Cult of the Dragons have halted their (current) plans of taking over the Mythal of Myth Drannor.
(For those of you familiar with the Shades) The group carefully made it back to the Castle that the Cult was stationed in (the name escapes me atm) and found a rather large black bubble off into the distance, roughly 3 blocks away.
They immediately teleported back to their base to tell their authorities (Harpers). Since obviously an encampment that size was too much for 3 people.

I plan on having a war between the Harpers and the Shades to uncover and put together the Arm of Valor and the other Arm (which will bring me to question 2). For those of you who had the 2nd ed Myth Drannor set you'll know just how powerful the Arm of Valor is.

My 1st question is: How do I handle a full-scale war that the PCs will, too some degree, control as generals. I don't have Chainmail or Warhammer so please don't make those suggestions.

My 2nd questions is: In the Myth Drannor box set it stated that the Arm of Valor is 1 of 2 powerful Arms... what is the other one and what functions did i have? If I can get an answer to this one, I plan on dragging out the plot and making it a race for both.

I greatly appreciate any suggestions. If this wasn't detailed enough just let me know.

Thanks again,
Telor

 

[Brix]

1. As far as I understand, the Harpers are a secret organisation, which operates much like secret agents / undercover agents. They have many of these loners in their ranks and nor an entire army.
I would do the following:
Let someone other make the war. Just describe what is happening and let the players run into a couple of small skirmishes. A lot of these small battles can give an idea of a big fight. Do this as long until the PCs start to complain (that's war) and then one more time (for cruelty reasons)
Let the PCs do something behind the lines: a distraction maneuver, or they have to persude / bargain another power group around Myth Drannor to help destroying the enemies...