Hospitals are assets that can be conquered in Warzone Idle.
Hospitals allow you to retain some armies every time you capture a territory. Their effects are doubled when capturing within four territories of the hospital. Hospitals take 2 hours to upgrade.
Hospitals take effect over the entire map. The total amount of armies you retained is the sum of the effects of all your hospitals.
Hospital reductions are applied before Joint Strike is applied. Your hospitals reduce the cost of the territory and Joint Strike calculations are applied to this reduced cost.
A territory that is more than 4 territories away from any hospital, will retain the sum of the base amount of armies saved by your hospitals after your capture it.
If a territory is within 4 territories of a hospital (in this case the 3rd hospital from the image above), you can see the effect of that hospital is doubled from 2.29M to 4.58M. This results in an additional 2.29M armies being retained when capturing that territory.