Would you be willing no elaborate on what you mean by "standard European model"? In the past century or so, there have been quite a few significant changes in how states and governments around the world, organized and equipped themselves for the business of organized violence.

I'm not a military historian but I will have a stab at an answers, although as I've studied British history I confess that my answer may have some bias and I can't comment on other western military powers, such as Prussia.

I would argue that the modern military structure had its routes with Napoleon, who was able to able to organise his army to be more flexible and reactive than previous armies and laid the ground work for the total war that dominated the 20th century. This was achieved by the French Republic establishing an effective civil service allowing him to better administer his troops; promoting officers on merit rather than patronage; and his most import innovation was organising his troops into corps. These were self supporting units, which could be deployed as seperate armies or united into one larger force to defeat another major army. The corp system meant his army was easier to supply and allowed his army to march faster as they could take a number of different routes to a battle and then it could combine just before the battle. This was quite different from other European armies that marched as one Army with seperate regiments of foot, cavalry etc and also had a larger amateur element to their armies. Theses innovations were then gradually adopted by other European armies.

The regimental system predates Napoleon and I'm afraid I don't know that much about it's origins, I believe it was a more gradual evoloution but I would place its creation in the 17th century. During the English civil war regiments were raised and maintained by individual Lords when neccesity required and were effectively mini private armies. They had their own uniform, miltary standard and training regime and soldiers were often more loyal to their lord than the army overall. These were under the authority of the overall Military commanders, but proved to be rather unreliable, lacking some displine and were prone to dessert the battlefield. This resulted in Oliver Cromwell forming the New Model Army, which was a centralised and proffesionalised army. The new model army enforced strict military discpline, regular training and gave a greater emphsasis to merit on the battlefield. This then looked much more like modern regiments under a centralised command, that could be more effectively deployed by a general.

Overall I think that the industrial revoloution is why western military system prevailed, the heavy technological advantages allowed for the creation of European empires and meant that for a while at least Europe would dominate the world. I believe that before the industrial revoloution the differing armies of the world were much more evenly matched.

The world wars caused a lot of innovation of technology and this seems to me to be the main driver of reorganisation in this period, such as the creation of the airforce and military inteligence become a much larger part of miltary expenditure. I don't think the underlying structure of corps, regiments etc changed that much during this time, but military tactics and strategy changed dramatically to take advantage of these innoations, such as blitzkreig.

I have of course missed out naval structure, but I think this was quite distinct from the structure of armies that your question was slanted towards.

I would also agree that the nature of warware is evolving and has become much more fragmented, covert and less formalised in the last twenty years, I think now western military structure is struggling to adapt to this change and could well radically alter during this century. I would guess that as special forces become more prevalent and operations more specific the layers of a military organisation are less important. Now miltary headquarters can view operations on the ground in real time and manage them more directly, so maybe the modern miltary structure reflects the conservative nature of the military rather than its operational needs.