ALTERNATIVE HISTORY: Khal Drogo vs Robert [spoilers PUBLISHED]

Let's say he invades like he promised he would - does he manage to topple the Robert regime? There is no war between Stark and Lannister yet.

The only direct defectors, imo, would be the Martells. Robert has the North, the Riverlands, the Stormlands, the Westerlands, the Reach (reemember - they basically sat at Storm's end feasting until the Targaryens were close to extinction ... and in this case they see 99 % dothraki coming at them) and only the Martells and Greyjoys join them.

The Iron Fleet could perhaps even transport them. Balon told Robert "You may take my head, but you may not name me oathbreaker. No Greyjoy every swore an oath to a Baratheon." which indicates that he has some care for oaths. But he is bitter, stupid (whatever Danaerys promise him in return, Drogo will smack him in the face when he mentions it) and the Ironborn are quite similar to the Dothraki.

Robert has better generals (Ned, Tywin, Tarly, Robb), he has the best fighters in the world. After some time of dothraki victories they face off against all the chivalry of Westeros and they scatter.

I believe this could strengthen Robert's reign since it's an existential threat to everyone. Varys definitely tells way ahead of the invasion.

The dothraki probably lands in the Reach because Dany be says they are her friends. The Targaryen loyalists ( who didn't bother to join when their crown prince was killed).

Robert becomes happy and drops 100 lbs n a year. He's like 36 so probably as strong as when young. Remember, when he hit Jamie - who is in very good shape and trained to always be ready) in aGoT, Jamie fell to the ground.

Results: Danaerys taken prisoner. Unless Tywin gets his hands on her. Cersei is poisoned by Varys or the Tyrells. I don't want to think about it and must not because Robert would likely kill Varys if he urged him to marry her. If Robert dies, it's probable Renly would be happy to take her to as wife. Khal Drogo slain by Jamie or Barristan.

Stannis inflicts severe damage and a good chunk of the Dothraki host drowns. Dragonstone is pillaged and the Dothraki gets bored because of lack of riches.

No matter who wins, Balon and the Greyjoys are NOT forgiven.