Emblems/numbers and placement/rank
The number you place on your vehicles represents your placement.
You are expected to place the number on the vehicle in a visible and obvious place. Best to put it on the side or tops of tank hulls or the back or sides of the turret. On planes it is best places on the side of the cockpit or somewhere on the tail, or the rudder. Please double side (unless on the top of the hull or back of the turret).

0 = Novice, new to squadron and in-training.
Squadron leader emblem = Squad Leader.
Wing commander emblem = 1st lieutenant
1 = 1st member in squadron.
2 = 2nd member in squadron.
3 = 3rd member in squadron.
4 = 4th member in squadron.
5 = 5th member in squadron.
6 = 6th member in squadron.
7 = 7th member in squadron.
8 = 8th member in squadron.
9 = 9th member in squadron.
Blue shield backboard = Blue leader
Red shield backboard = Red leader
Symbol of the 14th Panzer division = Yellow leader

Squadron leader emblem = The Commander of the entire squadron.
Wing Commander pennant = CoCommanders of the entire squadron.

All squads have a squad emblem, the squad emblem is applied to the primary vehicle(s) by the squad members, detachment squad members, Commander and CoCommanders.
Squads are restricted from using any emblem following:
The Squadron leader emblem
The Wing Commander pennant

An emblem used by another squad
An emblem that can only be obtained by premium purchase
Victory marks
Digits

In War Thunder, members are given the following ranks:
Regiment leader = Deputy
Squadron leader or Regiment Co-Leader = Officer
Member = Sergeant
Novice = Private
Moderator = Officer