Greetings!
Well, it seems to me that there are indeed classic strategies and tactics that will still remain useful--even vital--in a fantasy campaign. The brilliance of our own world is inspiring in it's own right, and, in similar circumstances in a fantasy world, against whoever as opponents, there is no reason to believe that the brilliant tactics and formations of our own past wouldn't remain just as brilliant, and just as effective.
However, and this is going to be campaign-specific, the level of magic available is going to obviously have a serious effect. However, the deployment of magic can also enhance the essential tactics and formations.
D&D hasn't really detailed the effects of magic--both spells and equipment--deployed on a large-scale battlefield. It amazes me that after all of this time--two years for 3E, more for the rest--that this issue hasn't been developed in detail. This is such a critical issue, and one that is prevalent in most campaigns, as most campaigns have large military operations eventually, that its neglect does present problems, as we see here.
To my mind, though, I simply do the work of integrating the best historical tactics, and combine them with magical effects. The generals of the fantasy world are not stupid. Where a standard tactic would work best, they would do so. Where magic will make such a tactic useless, then they would not employ such. And where some form of new tactic is needed, it isn't unreasonable to assume that that, too, would be developed and deployed.
The thing that just escapes me is how so many people seem to somehow assume that the fantasy world remains static. For example, suppose you start out with a fairly typical magical-medieval world. With kings and such having *knowledge* that magical power exists, well, even if they didn't have the talent or resources available to exploit such fully, they would begin to set up a system so that their children, or grandchildren, would, in fact, be able to exploit magic fully. And yet, year after year, campaign after campaign, noone does anything different with magic. Everyone just continues along holding on to the same old assumptions--"clerics only heal those who are favoured" "Wizards are old, and like to stay locked up in some isolated tower in the middle of nowhere" "Rogues are always greedy and self-serving" and many, many more.
Give it five generations, and there will be magic everywhere, in big ways or small. This, over time, would have great impact on military operations. Like with standard technology though, for every offense, there is a defense, and magic would be no exception.
It shouldn't be far-fetched to assume that armies would routinely deploy invisible, hasted Rogues. Or Rangers. And so on. Flying columns of cavalry, assault wizards, as well as even normal horses routinely augmented with magic horseshoes or haste, and so on. Magic communications would vastly change the dynamics of military operations. The side who had better command and control over their forces would have the advantage over the side who didn't.
Battlefield healing and medical evacuation would be far superior. Even if say, there isn't enough clerics to instantly heal everyone. So what? You may very well have hasted, multi-legged medical golems that can load and carry wounded soldiers to field hospitals where surgeons can begin work on them. While riding inside this thing, healing gas would be emitted into the chamber to keep the dying character stable. These battlefield hospitals could greatly enhance the disease resistance, poison resistance, and wound recovery of normal soldiers without the direct actions of powerful clerics. These centers could do so with magical equipment and the presence of trained physicians, surgeons, and healers. Think of how these developments alone could change the way and consequences of warfare. Again, though, these kinds of developments would most likely come along with urbanized, wealthy, sophisticated societies. Less organized realms would not have the power, resources, organization, or coordination to have such refinements. Imagine these differences being in stark contrast to a confederation of Orc tribes waging war against a powerful, sophisticated human kingdom.
It is integrating rather modest levels of magic, but on a mass scale, that would significantly effect military operations and capabilities. The fantasy battlefield would bear a closer resemblence to our own complex battlefields, and yet, in our modern warfare, many of the ancient tactics remain valid and brilliant still. They are enhanced, rather than negated, by modern technology. Similarly, magic would most often enhance many of the older tactics and formations.
Semper Fidelis,
SHARK
