Why do Enlisted use a higher number in their call sign?

Way back when I was in CAS3, I did one of those short weekly papers and had to delve down into the history of call signs. I'll have to dig it out, but from what I remember the use of 'usual numbers' for the unit positions started after WWII.

One supposed reason the “6” became associated with the commander is that the brigade/regiment was lowest unit level which had its own radio net. The commander was an O-6, thus "6" on the radio. This was actually the reason for my paper ("military myth or historically accurate?").

Personally, the reason I believe it became a common practice for the call sign was because back then Soldiers were really no different than today – it’s a lot easier to ‘modify the wheel’ than it is to ‘create the wheel’ and examples in FMs are frequently used as "the right way" for doing something.

During my trips to the CGSC library (most resources are all online … now *sigh*), I was able to dig up a War Department FM on Signal Communications (FM 24-5*) from 1942 and declassified operations orders used during that timeframe.

The cliff notes version is that field telephones were used more than radios (and were the preferred method of communication), the telephone directory rarely changed, and the numerical designator given to the individuals in the unit's SOI for the most part copied the example telephone directory in the FM.

Since commanders were usually called “XXXXX 6” (and everyone was used to calling the commander by that call sign), it carried over into FM communications as well. Now “6” for the commander has become one of those unwritten military traditions.

As an illustrative point, I’ve attached the example from the old FM and extracts from the 38th and 84th Division's SOI from the early 40s).

Specific to the question of why do enlisted use a higher number in their call sign – that’s actually local policy that has developed its own unit traditions over time. I assume that sometime in the past, either a Commander or the unit's Signal Officer, decided to replace the traditional number designator for the Adjutant with the senior NCO (especially since the isn’t an Adjutant below division).

People move on ... others like that idea and it starts spreading … the Commander gets promoted to higher command positions and maintains “My senior NCO is ‘7’” … etc.
------------------------------------
* https://cdm16040.contentdm.oclc.org/digital/collection/p4013coll9/id/817/rec/4

I carried one or more radios for the majority of my career, and I never found a documented reason for this. I always assumed that it allowed for the maximum number of call signs available for sub-units for that commander. It gives a company 4 call signs for 4 platoons (and 5 for the XO).

As best I remember, we stopped using those type call signs after the RVN conflict. Too easy to compromise, and the CEOI started using random call signs that changed every 24 hours.