The War Department is a Tier 3 government building in Civilization VI: Rise and Fall. It is built in the Government Plaza district and requires a Tier 3 government (Communism, Democracy, or Fascism) and a Tier 2 government building (Foreign Ministry, Grand Master's Chapel, Intelligence Agency, or Queen's Bibliotheque).
You'll want to build the War Department if you're trying to win a Domination Victory. It provides free healing to your units with each kill, helping your army and navy stay fighting fit.
Civilopedia entry Edit
The War Department (or its euphemistically-named counterpart the Ministry of Defense) vies with the Foreign Ministry for the title of "most important office of the head of state." It is the result of the confluence of a number of forces: The increasing complexity of governing, the rise of the professional military and the staff officer corps, and the realization that putting an unchecked, charismatic warlord in charge of the military can lead to bad consequences for the government's long-term survivability. To a student of military history, it is remarkable how the once-controversial notion of civilian control of the military is now effectively codified across the major nations of the world.
Today, the United States' Department of Defense is the largest of these War Departments. Headquartered in the mammoth Pentagon building on the outskirts of Washington D.C., it is the world's largest employer, oversees the largest military in the world, and spends the largest military budget of any nation (exceeding more than the next dozen or so militaries combined).