“With generous financial investement, the army can research, develop and train new and better units to fight for Tartesia on the battlefields.
Even though it may take some time, do not forget to assign the new units to your army when they are ready.”
It is possible to research evolving and upgrading your troops. Upgrading troops costs gold and takes time (possible to be speeded up by diamonds).
By doing the research, you make it possible to evolve the troops (if it is a new unit tier upgrade) or just make your current troops more powerful.
There are 3 main races in the game, and each of the 3 races has their own units, all divided in 4 unit types: warriors, mages, shieldmen and rangers. You can navigate by pushing the buttons on the right (for races) and on the left (for unit types).
Human units are considered as weakest, so they cost less and take less time to be evolved.