I didn’t say the Vale was weak. I said that it was one of the most thinly populated provinces. It’s troops are among the best, having served under King Robert’s highly experienced Hand, John Arryn, Lord of the Vale and Warden of the East, They don’t have the population to field a military force of the same size as some of the other provinces however.
True. Of course I’d argue that the Westerlands were also untouched by the first two (it’s the Crown that took on the debt, not the Lord of the Westerlands) and only very lightly touched by the third (Rob never got past the northern edge of the Westerlands before his assassination), and has had more than enough time to recover since.
The Vale and the North combined probably have the most skilled and experienced troops, but Cersei can certainly field more, even if they may not be quite the same caliber. The problem for the Northern forces however is that they dare not throw everything they have at Cersei. They’ve got White Walkers just waiting for an opportunity to either break through the wall, or march around it on frozen ice covered seas. In fact, Sandor’s vision in s7e1 appears to imply the latter.
The Westerlands aren’t appreciably weakened, and they started out far more heavily populated and economically stronger than either the Vale or the North. They also have had the benefit of some of the best military leadership. Could the united forces of the Vale and the North defeat Jamie Lannister’s troops? Possibly, but it wouldn’t be either quick or easy, and the White Walkers would likely kill everyone before a winner could be determined. Could Dani single-handedly defeat Jamie’s troops with just her unsullied and dothraki? I doubt it. OTOH, if everyone (Dani, Highgarden, Dorne, the North, and the Vale) dogpiles Cersei, then she’s a gonner, and it’s increasingly looking like that’s going to be exactly what happens if Euron doesn’t knock out or at least tie up some of her opponents.
And I completely agree that the dragons make it much much easier for her to conquer all of westeros, assuming she can control them.
This discussion has motivated me to look for the ep from last season where they were calculating how many ships Dani would need to get her army to Westeros. I vaguely recall that the size of her force was discussed in that context. I’ll chime in on that point once I’ve found it if someone else doesn’t chime in on it first.