Smithery is a Tier Three technology after Mining in the Climbing branch that allows you to build forges and unlocks the swordsman unit. It is a Economic and Militaristic tech because of the forges and the Swordsmen unit.
Forges produce 2 population for the city's in which borders they are in for every nearby mine horizontally, vertically and diagonally in a range of 1. The mines don't need to be inside the borders in order for the forge to count them. You can only build one forge in each city.
The Vengir tribe starts with this technology.