Just some more loose ends. In the US Army, you can address a Sergeant First Class (E7) and a Master Sergeant (E8) a “Sergeant”, but a First Sergeant (E8) is addressed as “First Sergeant” or “Top”. There is only one E8 in a line company and he the First Sergeant. (Headquarters companies may have multiple E8’s, but only one 1SG.)
Sergeant Majors or Command Sergeant Majors are both addressed as “Sergeant Major”.
A Corporal (E4) is a leadership position, but a Specialist (E4) is not. A team leader is usually a Sergeant (E5), but if you have an E4 filling this slot he could/should be laterally transferred from a SPC to a CPL. It is not required, though. Being slotted to go to corporal may also accelerate this soldier’s attendance at the 1st NCO leadership school. The CPL is and NCO, the SPC is not, so the CPL will out-rank the SPC if they are ever performing a mission together.
Line Company, Chain-of-Command positions
SGT, E5: Team leader (3-5 soldiers)
SSG, E6: Section leader/Squad leader (2-3 teams)
SFC, E7: Platoon leader (3 squads)
There are multiple (3-6) line platoons in a line company.
The SFC reports into the Lieutenant (2LT or 1LT). The number of people in these elements various depending on the branch within the US Army (Infantry, Signal Corps…)
There are staff and support positions in the headquarters platoon (supply sergeant, operations sergeant, NBC sergeant…) that have E5 and E6 ranks, too.
Once a soldier hits E8, he is out of the chain-of-command. Most of these positions are staff positions involving planning or logistics. A select few of these positions are slated as advisor-to-the-commander positions: First Sergeants for companies and Command Sergeant Majors for everything above that (battalion, brigade, division, corps…). While these NCOs reports into their respective commanders, they are also collectively referred to as the “NCO Support Chain”. As stated above, they are tasked with ensuring high morale or at least with solving problems that could cause low morale (pay problems, disciplinary issues, ration support…). They also, via various groupings, decide how NCOs are going to be promoted and what the requirements for promotion are going to be. (The officers must approve these decisions.)