An anonymous commenter made an excellent point recently (such that I broke my rule of not publishing anonymous comments):
"There are many, many examples in history of bitter factional conflicts in which one side (or both) invite foreigners into the country in order to destroy their domestic enemies. The foreigners inevitably destroy one faction, then the other, and never leave. This has happened so often that one can only conclude that it is human nature to develop such a blinding hatred of your domestic foes that you would do anything, including hand over the country to foreigners, rather than see your domestic foes win"
Politics is simple and binary at the level humans can understand it
(i.e. politics is either simple or incomprehensible);
and any social group gets cohesion primarily by exclusion.
We define ourselves and our allies primarily in terms of who we are not.
Therefore, as domestic politics becomes more conflicted, and the perceived gulf between who we are and who we are not becomes (apparently) wider; a point is reached at which anything seems justified in order to defeat the enemy (not least because the situation has become so polarized that we are rightly terrified of what the enemy will do to us if we are defeated).
At that point people make a grab for the One Ring using the-end-justifies-the-means arguments
(i.e. that 'nothing could be worse' than being defeated by the domestic enemy).
And that is when a group invites the alien powers, the mercenaries, the irresistable machinery to help them win the war they cannot contemplate losing.
So - here's are some questions to consider:
Which side is ramping-up the conflict?
Which side is most terrified of losing?
Which side has invited the alien powers to help them win?
To ask these questions is to know the answers.
We have - in other words - already passed that point in which one side cannot contemplate losing the domestic battle and would therefore sacrifice anything and everything to win it.