Topics: Matchmaker (WoT) - Global wiki. Wargaming.net
Team selection for random battles is done according to several parameters. Each battle takes place in a battle tier , which should not be confused with tank tiers. (On this page we always use Arabic numerals ("7") when discussing battle tiers and Roman numerals ("VII") when discussing tank tiers). Team balancing within a battle tier takes place according to vehicle specific weighting and additional restrictions.
Battles can take place in ten different battle tiers. Each vehicle, depending on its performance, is assigned a certain subset of these battle tiers that it is supposed to fight in.
The selection of the battle tier you fight in depends on the amount of players available for each battle tier and is otherwise random.