Sitting back looking at mankind's history I feel there are two constancies – sex and violence. Maybe prostitution and warcraft are one of the oldest professions in human history, right after hunting and farming. In terms of warcraft I'm not sure how Ötzi and Conan were rolling but records of tactics, procedures and technology go back into pre-biblical times with the Babylonians the earliest.
This is as humans are structuring their world and change it according to their needs. A well-documented example is the hoplites back in the merging of European culture. They´ve been a large group of men with shield and long spears. The individuals of the formation were connected to their frontman through their shield and the spears in between the rows to the front. So when released there was an unstoppable force charging at its enemy with a meters long wall of pikes to the front, driven into flesh and leather as well and in the end overrunning the individual, no matter what fierce fighter he has been. The sheer mass to outplay bravery and individual skill. With new inventions in technology, tactics changed.
One remarkable development is for sure the firearm. This changed the battlefield forever and melee combat lost it´s relevance more and more. Even here you can see the change from the formations of line-infantry to ranger units (Jäger, Chausser, etc.) as the rifles were becoming more precise, reliable and cadence increased. Now we are in the present and the state of the art in infantry tactics are SOF, starting to develop in WW II. When Skorzenzy had nothing than a bunch of daring men (of course battle-hardened then), a Jaegerkorps soldiers schedule might be very down to the point until he is ready for deployment. Again humans want to structure their world.
I grew up with Small Unit Tactics know as something clandestine only the chosen ones (fucking hell week) get to know, but still, things stayed misty. Later my career I joined a scout platoon where I recognized that there are parallels and also a need of professionalization. For me, it did not matter anymore what was the name of the brand (I grew one or two years older). Of course, not everything is applicable as a scout´s platoon obviously doesn´t need a DAR-corridor.
His E&R is to get back to his battalion. But also in regular infantry units, I could see a trend in the development of techniques, tactics, and procedures with the availability of technology. In my early days as a paratrooper, we were trained as a 12 men Squad all rifleman and some special roles. Looking back at my last deployment things changed a lot. At first, there was no squad anymore, now we were an operational team (maybe fireteam sounded to aggressive for some of the NATO-armies. Then we had more technology and more equipment we could use at once.
This six-man team could choose its setup from light machine guns to an anti-material rifle. Following this, for us at PG it is logical that tactics are changing too. This is how we see Small Unit Tactics. It is not clandestine, and not just for some chosen ones. Instead, it is the basis from where team tactics are build up. Just like a pyramid built with a solid foundation. The difference to SOF is made somewhere else.