The hour of judgment is close at hand as the Orcish Hordes stand ready to sweep across this domain like a pestilence and seize the capital of Lordaeron. Standing vigilant above the plains like the descending arm of twilight itself, is the Violet Citadel of Dalaran. The Citadel - serving as sanctum and haven to the Mages of Lordaeron - is the last barrier between the Orcs and their subjugation of Humanity. Manifested in the combined magical prowess of all Mages within the Alliance, this place must fall for the Horde to conquer Lordaeron. Fortunately, Orgrim Doomhammer has saved his greatest weapon, ready to unleash it upon the unsuspecting Alliance at just this moment - Dragons.
Objectives
Destroy Dalaran
Destroy the Alliance's defenders
Battle
Background
Note: this account comes from the Official Strategy Guide, which features a first-person description of each mission from the game.
Dragons indeed were the main weapon in the conquest of the island, but first Urok's forces had to raise a city to support their production. All of their military units swept quickly southward and removed all the defenders near the gold mine; the construction of the necessary buildings were begun in earnest. During this time, they erected many guard towers to deal with the constant harassment of enemy gryphons; a shipyard went up to produce oil tankers and destroyers for the same purpose.
When they started running out of gold, they assaulted the southern outpost to get peons beyond it to another mine. The first step of this operation was to send a single sapper to blow up the western tower. With the task out of the way, they rolled catapults to remove the rest, escorted by more troops, and the way was cleared to start another great hall and plunder its resources. Another shipyard went up near it, to launch more destroyers on that side of the land bridge for defense against gryphons. By that time, they had four dragon roosts started. Soon the skies belonged to them. The assault on the island required the combined efforts of dragons, catapults, and ogres. The dragons did most of the destructive work, but catapults and ogres escorts were required to take out enemy guard towers, which could fire on them. Sappers also came in handy for a few of them, but most structures fell to the catapults while the dragons worked on mobile targets. With careful and constant strikes on single targets, each followed by a brief retreat, it was only a matter of time before the island was theirs. Urok believed, that very soon, they would be able to say the same for the rest of the world.[1]
Aftermath
This battle was a painful loss to the Alliance. Though razed by the battle, Dalaran was quickly rebuilt, and continued to function until its complete destruction at the hands of Archimonde in the Third War.