WT has its tanks in ranks
Rank I is starter, these vehicles are bad, and have zero armor.
Rank II, some nations get better guns and more armor, some get more armor, but get bad guns.
Rank III, you get into mid-WWII tanks, Tigers, T-34s, KV tanks, M4 shermans.
Rank IV, you go into late WWII.
V, you go into the start of the cold war, and get access to helicopters if that nation has em.