The Legion as we all know are launching their biggest invasion ever. Every major faction on Azeroth would suffer, not just the alliance and the horde. The Legion has thousands of demonic fleets, each thousands of demonic ships that houses hundreds of demons while larger ships and flagships could house up to hundreds of thousands of demons. The Legion will send at least tens of millions of demons during the first few hours alone. They would continue to reinforce their first wave of invaders through countless portals. No details about their total numbers but it is hinted that they have enough numbers to conquer Azeroth hundreds of times over.
Alliance will lose around 3,000,000 - 3,500,000 troops with around 2,500,000 troops lost during the Broken Shores alone. More than 50% of these numbers will be human deaths.
Horde would lose around 2,700,000 - 3,100,000 troops. Over 2,200,000 horde troops will be lost in the Broken Shore event alone with 70% of them being Orcs.
Zandalari Trolls will lose around 1/3 of their total military force fighting off the Legion invaders on their island which is around 2 million troops.
N'raqi will lose around 4 million to 5 million of their numbers trying to fight off the Legion Invasion.
The Naga will lose around 3 million of their troops to the Legion.
The Nerubians will lose around 7 million of their troops to the Legion forces.
The Qiraji will lose around 3 million to Three million five hundred thousand of their warriors to the demonic invaders.
The Undead Scourge will lose over 3 million of their troops to the Legion.
The Illidari will lose around 1,000 - 1,400 of their guards to the Legion.
The Pandaria continent will suffer a total of over 20 million deaths from the Legion Invaders, counting the Mantid, pandarians, and Mogu alone with the other natives there.
Dalaran will suffer around a few hundred thousand deaths during the course of the Legion Invasion.
Twilight Hammer will lose around 1 million of their cultist during the Legion Invasion.
The Elemental forces will lose around a few million of their troops to the demons.
The Dragonflight factions combined would lose around 800,000 dragons.