West City is a city in the western region of Amestris and serves as the military command headquarters for the area. Though little is known about West City and the area under its jurisdiction (as it is the only region of the country not directly visited by the Elric brothers) what is known is that - in the manga - West HQ's forces are frequently in direct conflict with the neighboring country of Creta over the location of the national border. Western military forces are also said to have an impressive number of troops, all adept in guerrilla warfare.
In Chapter 52, when Colonel Mustang's group is forcibly disbanded by the Führer, 2nd Lieutenant Heymans Breda is reassigned to West City's HQ, where he discovers that reckless military strategies have led to a massive death toll in the current border war in the town of Pendleton.
The Western Military seems to have a strong affiliation with Central City's forces, as West HQ is the only region to send military aid to Central during Roy's coup d'état in Chapter 89.