The Last Valley

"The Captain" (Michael Caine) leads a band of mercenaries who fight for the highest bidder regardless of religion. His soldiers pillage the countryside, and rape and loot when not fighting. Vogel (Omar Sharif) is a former teacher trying to survive the slaughter of civilians occurring throughout south-central Germany. Vogel runs from the Captain's forces, but eventually stumbles upon an idyllic mountain vale, untouched by war and still living in the age before the war.
The Captain and his small band are not far behind. Trapped in the valley, Vogel convinces the Captain to preserve it and the village it shelters for their own benefit, as the outside world faces famine and devastation. "Live", Vogel tells the Captain, "while the army dies." The Captain decides that his men will indeed rest here for the winter. He forces the locals to submit, especially their Headman, Gruber (Nigel Davenport). The local Catholic priest (Per Oscarsson) is livid that the mercenaries include a number of Protestants (and nihilistic atheists for that matter), but there is little he can do to sway the Captain. The mercenaries are of one mind after the Captain kills a dissenting member of his band, and religious and ethnic divisions are set aside.
At first, the locals accept their fate. Vogel is appointed judge by Gruber, to settle disputes between villagers and soldiers. As long as food, shelter, and a small number of women are provided, the mercenaries leave the locals alone. Hansen (Michael Gothard) attempts to rape a girl and, exiled from the group, manages to lead a rival mercenary band to the valley, before the winter sets in and closes the valley to all outsiders. He and his band are destroyed and the valley goes into hibernation. But as winter fades, it becomes obvious that the soldiers will have to leave. The Captain learns of a major military campaign in the Upper Rhineland and decides to leave the valley in order to participate. Vogel wants to accompany him, fearing Gruber will have him killed once The Captain leaves. However, the Captain orders Vogel to stay as the condition of not sacking the village, leaving a few men as guards.
After the Captain departs, his woman from the village, Erika (Florinda Bolkan), is caught engaging in devil-worshipping witchcraft. The priest orders her tortured and burned at the stake. Enraged and realising the evil that has destroyed so much in this war (religious fanaticism) and the role he played in it, one of the Captain's men sacrifices his life to kill the fanatic priest by pushing him into the fire (beginning of the age of enlightenment). Meanwhile, the Captain and his men engage in a major siege operation. Most of his men are killed. The Captain survives long enough to return to the valley, only to find himself faced by the villagers. Vogel intervenes so that no fight happens. The Captain reports the event and dies of his battle wounds, declaring to Vogel, "You were right. I was wrong." A young woman from the village wants to leave with Vogel, but he tells her to stay, and runs off alone in the mist, satisfied at having saved the valley.

Question: Where is the military campaign that causes the soldiers to leave the village?
Answer: Upper Rhineland