Higher levels of the Blacksmith/Armory unlocks higher-level upgrade for Barrack Troops, whereas upgrades for War Tactics, Factory Units / Troops, and Airstrip Units require upgrades to the War Academy, Factory and Airstrip respectively and do not depend on Armory level. For example, it's common to move to Factory troops at Global Age (and above) making it unnecessary to upgrade the Armory building beyond Industrial Age.
The Armory starts out as the Blacksmith at level 1 to 5 and adopts the current name starting from level 6.
The Blacksmith is first available in the Stone Age.
Reduce cost of Army building upgrades by 3,000 ~ 80,000 Food/Gold (to a minimum of Free)
Trivia[]
A second upgrade slot can be unlocked for 1,000 . It is a permanent 2nd upgrade slot that allows two simultaneous upgrades, and this is considered the most useful use of crowns in the game (functionality added in version 5.3 long ago).
Certain events decrease the second slot cost of 1,000 to half (500).
The Armory building level only dictates which Barracks troops can be upgraded; Airstrip and Factory troops need to be upgraded there instead. For example, an Industrial Age Armory can upgrade Information Age heavy tanks if the main Factory is Information Age level. Same applies to Airstrip, War Academy, Embassy, and so on.