But the feminist element (though perhaps a bit overdone) is important--and suggests that perhaps there would be fewer wars if women (not women pretending to be men) were in charge.
Part of the problem, I think, is that there are few obvious passages that actually state this point specifically--that's not the way Pratchett writes. But the overall "message" of the book, I think, is that Polly (and perhaps Maladicta) have learned something very important from their experiences--that what Polly has learned (see pp 315-316 in British hardcover) is that she is a soldier, not someone to be patronized by a woman masquerading as a man general, and dismissed as "my dear". It is through the efforts of this group of women, and the "ghost" of the Duchess that this war is ended.
On p. 317, the Duchess says that they are heroes who would willingly die for her in battle, but now she demands something more--"You must refrain from dying in battle. Revenge is not redress. Revenge is a wheel, and it turns backwards. The dead are not your masters." Polly, in the meeting with Vimes manages to suggest terms that leave the country some pride, but at the same time silently acknowledges the stupidity of what the war has done to the country.
Some six months later, things are quite a bit better--they have survived the winter. But as Vimes had warned (328-329) Prince Heinrich still isn't the ruler of two countries--but he still wants more. He wants the power and influence of Ankh-Morpork, but he doesn't want to earn them, or grow into them or learn how to use them. He just wants them. And sure enough Prince Heinrich is trying to claim Borogravia again.
And Prince Heinrich must be stopped, so Polly can go back to doing something she has learned from Sergeant Jackrum, and from her total experiences. She has learned that wars need not be fought stupidly. And what she has learned is (p. 352) "The enemy wasn't men , or women, or the old, or even the dead. It was just bleedin' stuipd people who came in all varieties. And no one had the right to be stupid." Not even Prince Heinrich.