There were only 50,000 Alliance members left alive after the fort collapsed!
This happened because close to 85,000 alliance members died with the explosion of the fort. The archballistae's had an kill rate of 150 and about 20 were injured per minute , they ran for close to an hour , and there were ten such archballistae's , making the total death count under the arrows to be close to 90,000 . Also an additional 12,000 had been injured.
Also under the assault of Medivh , the bombs , the archballistae's mounted on the pirate ship , the cannons fired , the arrows shot manually by Elite guild members , and the members that died under the swords and shields of the tanks , the final death toll came around 25,000 troops.
The massive army of 2,50,000 had been reduced to 50,000 . The collapse of the fort was a masterstroke that no one saw coming.