In the unit overview you can see your 3 units shown. Below each unit avatar image is:

White bar = morale

Blue bar = life points

Yellow bar: Unit XP towards the next rank up (Whereby dark yellow is secured, light yellow you lose on the next death)

To the right of this bar is a rank icon. As known from other Total War parts, your units can increase in rank and thereby receive significant buffs on your statistics.

Rank 1: +10% Melee Defense, +10% Melee Weapon Damage, +10% Melee Attack, +10% Impact Damage, +10% Body Armor

Rank 2: All stats at 20%

Rank 3: All stats at 30%

Rank 4 (Star): All stats at 50% 50% that's a tremendously powerful buff. So pay attention to the opponent's rank when you're fighting!!