That's a great question and worthy of a deeply researched book. Keeping it simple, however, I have a few thoughts.
Historically in our western society (well after tribal society at least), officership had originally been tied to class status. A good example is the Roman system where the senior leaders, legates and tribunes were in fact political appointments generally reserved to the senior social classes, the patricians and the equites, as part of their climb through the cursus honorum by which high political office was earned. Under the Marian system armies were commanded by either the consuls or proconsuls of a province who picked their legates (commanders of legions) and tribunes (legion staff officers) from these two classes for any given campaign. Leadership in the ranks came from the centuriate who were professional soldiers who rose through the ranks to ultimately the tactical leadership of a 6,000 man legion under the "supervision" of a legate. Along the way a lower caste Roman in the army could hold numerous leadership positions which we could consider NCOs from tent group commanders (the equivalent of a section) to standard bearers, musicians, optios (second in command to centurions), and others. The lowest level of centurion commanded 80 fighting men (and 20 non-combatants although the number varied greatly - hence "centuria") and hence would probably be considered the equivalent of a company commander in our system. The centurions commanding a cohort (i.e 6 x centuria) would be the equivalent of a battalion commander and of the legion (10 x cohorts) the equivalent of a brigade commander. What's noteworthy, again, is that every centurion had risen from the ranks and his entire schooling learned on the job. Similarly there were no formal schools for legates and tribunes although some had informal education in tactics and warfare through tutors and gained some experience as they worked their way up the cursus honorum.
Cut to the post-Roman era where feudal systems created a different form of ruling class which also formed the backbone of the military leadership of any given kingdom. Again, military studies were an informal regime of studies of books (for those who read), tutors (for those who couldn't read) and practical experience. There were few standing armies (in fact for much of it's history, Rome didn't have standing armies either, raising and disbanding legions as needed) most being raised as needed from the various subject nobility that owed its allegiance and status to the king and hence these nobles formed the leadership. In many cases the various nobles would hire mercenaries experienced in war to form a loose subordinate leadership structure.
Cut again to the end of the middle ages and the demise of much of the feudal system and we find a the king cut out the middle men issuing officer appointments directly by way of a commissioning system whereby the individual officer swore his allegiance not to some lord in the feudal chain but to the king directly. A more formalized rank structure, independent of the feudal structure, became set. Notwithstanding the fact that military leaders were not required to be nobles, in almost every country, the nobility did form the vast majority of the commissioned officer class in large part because of their higher education, in part because most nobilities passed to the eldest sons and therefore younger sons needed to find employment, and in some cases because commissions needed to be purchased and only the high borne could afford the expense of being an officer.
With time, and industrialization, formal military education by way of war colleges found their way into the systems of most countries. While some countries retained the need to be "upper class" for it's commissioned officers for quite some time, others turned more to merit especially as commoners started to receive public education and were found to be the equals of their upper class peers.
For the most part, the rest of the world went through similar stages as western society.
Currently the main division as between commissioned officers and the other ranks is their respective education levels and other competence evaluation systems. While some countries require university degrees for commissioning, others still accept candidates from lower level, usually matriculation levels, but then put them through a formal officer commissioning education process (such as Sandhurst)
So. Why does the army take newly commissioned officers and make them platoon commanders. Simple. To give them the experience they need to round out their formal leadership training. At every leadership stage for Army officers, there is a formal education component coupled with a practical experience component up to and including battalion command.
Would warrant officers make better platoon commanders. In all probability, absolutely. But then where does the junior commissioned officer get his experience? One example would be the officer training regime in the German inter-war Wehrmacht. Individuals who were evaluated and selected for officer training would take the same basic training as other recruits and subsequently train for, attend schools for and serve in several layers of ranks which were the equivalent of specific NCO ranks (and in units alongside regular NCOs) all the while being evaluated for their leadership abilities. At any time they could be found wanting and remain "in the ranks". It is only after having gone through this lengthy schooling, training and experience and probation (roughly two years) and being considered acceptable that the candidate would be commissioned as a second lieutenant.
In many ways, those units had many more troop leadership positions for NCO and in fact most platoons would be led by NCO. German infantry regiments (typically three infantry battalions of three rifle companies and a machine gun company each, a close support artillery battery, a close support anti-tank battery, a signal platoon, two motorcycle platoons and a pioneer platoon) would have on their establishment only 48 officers but 316 NCOs and 1,644 privates. In effect, a rifle company had two officers and 140 other ranks. The officers consisted of one captain as company commander and one lt/2ndLt who commanded the first platoon and deputy to the company commander.
The lesson here quite simply is that you can easily staff many of the battalion level leadership positions with NCOs as long as you are willing to accept a lower ratio of officers to ORs (which also means a lower quantity of officers at the myriad of higher level staff positions - a situation which could be remedied by having more NCOs at higher level staff or a higher level of CFR'd officers there - both of which IMHO are desirable but are contradictory to the current "most commissioned officers must have degrees" policies) Again IMHO, considering how bloated our officer corp is, there is little appetite to change the system.
The Navy has a similar, albeit later, history as the Army. For most navies, however, navigation and sailing was, in many ways, a much more complex art than soldiering and there was an earlier drift towards education, especially navigation, than the Army. Post industrialization many of the same factors vis a vis an educated commissioned officer corp dictate the division between such officers and other, more technically oriented and skilled tradesmen other ranks.
I've never understood why the Air Force has every aircraft operated by one or more commissioned officers. We used to have flight sergeants and quite frankly I think that we still should and flight warrants could easily handle small tactical groups. We certainly do not need that many to feed the staff pyramids. More and more Air Force rank seems to be tied to pay and occupying the same mess rather than any leadership component. I presume much of it comes from the history of the formation of the air forces from volunteers amongst the numerous cavalry etc officers during WW1. Technical skill can easily be rewarded with pay supplements rather than rank while sufficient leaders to feed the system could be done through a limited number of flying status commissioned officers or through commissioning from the ranks.
425 Tac Fighter Sqn has 22 officers and 141 other ranks for give or take 12 aircraft; 436 Tpt Sqn has some 77 officers and 338 other ranks for give or take 17 aircraft; and 408 Tac Hel Sqn has 70 officers and 223 other ranks for give or take 16 aircraft. To me, that makes very little sense although I'm quite sure I'm about to get a heavy lecture on why an Air Force squadron needs more officers then the average infantry battalion (who are also already bloated).
Let the bun fights commence.
:cheers:
