In any discussion of military tactics and strategy the participants must state whether they are talking ‘Pre Korrilean’ or ‘Korrilean’ tactics and strategy.  The Emperor so revolutionized Solistan tactics that the distinction must be made.

To be clear, not everyone has adopted Korrilean methods, some Rulers and their Generals stick to the ‘old ways’ and it is certain that the Barbarians have not changed their ways, but even the Elves, with thousands of years of war behind them, have adopted some of Korrilean’s innovations.

Pre K
Infantry tactics were largely ‘phalanx’ based with large bodies of infantry, sometimes in the thousands, in at least three ranks (sometimes four or more) wielding long spears/pikes, large shields wearing breast plates with helmets and secondary arms of short swords were the dominant force on the battlefield.  Third rank troops often lacked breast plates, instead having, at best, scale and more likely leather or padded armor.
A battle opened with two or three volleys of javelins, thrown by the second and third ranks, with the first rank using their shields to fend off incoming javelins.    The two forces would charge each other, pikes lowered, and commence a titanic shoving match until one side gave way.
Supplemental light troops, usually unarmored slingers and archers, provided harassing fire that rained down on the enemy’s main body and tried to suppress the opposing slingers and archers.
Cavalry tactics involved trying to flank and sweep the enemy phalanx from behind, while driving off enemy cavalry and skewering as many of the unarmored archers and slingers as possible.  Cavalry was mostly medium, with lances and some form of hand weapon.
Rulers usually maintained the core ‘Heavy’ Infantry (the first two ranks) and forces of cavalry, between campaigns.  Calling up the troops of the third rank and the supplemental, from their country’s militia and spear levy when needed.  These forces usually outnumbered the Heavy by three or four to one, if not more, on a battlefield. 

Korrilean Tactics

The Emperor began his career as a common soldier, a ‘ranker’ in a mercenary company.  At one time or another he had stood in each of the phalanx ranks and had ridden with the cavalry and was himself a skilled archer.  From these experiences he orchestrated his changes.

The Emperor’s first major change was in breaking the solid line of the phalanx into anywhere from four to twelve (depending on the size of the battle and the terrain) smaller ‘Battle Groups’ which Korrilean referred to as his ‘Shields.’   
Each Shield was four ranks deep, all similarly armed and equipped.  The space between the Shields would vary slightly and would have a single rank of troops strung between the Shields.  The space between the  Shields always wide enough to allow troops to pass through. 
As the line of the enemy phalanx (or barbarian horde) impacted the Shields, their formation would immediately break up.  The enemy troops NOT hitting a Shield would advance forward, pushed by their own ranks behind them.  The single line of screening troops would fall back, melting into the flanks of the Shield formation to either side. 
The protruding phalanx troops would find themselves with no one immediately in front of them to stick their pikes into, but having the third and fourth rank of the Shield formation on their flanks carving up their unprotected and lightly armored backsides.
The Emperor’s ‘supplementary’ troops, mostly archers and crossbowmen, would pour arrows and bolts into the thinning ranks of the protruding phalanx, then move forward, finishing wounded enemy, and positioning themselves to shoot into the balance of the enemy force that no longer can form solid shield walls to block the hail of missiles.
The Emperor made changes in weapons and armor as well. 
Breast plates were largely replaces with scale or chain.  The javelins were eliminated and every trooper in the Shields were equipped with a quiver of heavy War Darts (see Weapons) attached to the inside of their shields.  A quiver held six darts and all ranks would throw them, both in volleys and at will.  This was a tactic that Korrilean had experienced when campaigning in Pallador.  This allowed for heavier and more frequent and sustained missile volleys. 
The crossbow, light cavalry crossbows and light and medium infantry crossbows, were widely used by Korrilean.   While it takes a life time to train an archer, a crossbowman can be taught the basics in an hour and be well trained in a week.  Volleys of bolts, shot by the supplementary infantry, would be coordinate with volleys of darts thrown by the Shields.  The enemy would be pressed to block both volleys at the same time with their shields.
Korrilean’s cavalry made use of light cavalry crossbows that can be ‘hooked’ on the saddle for cocking and reloading.  His mounted troops were now able to suppress the enemy formations of archers and slingers as well as thin out enemy cavalry without the chaos of actual contact. would sweep past an enemy formation, shooting at troops and thinning their ranks just before a second wave of lancers, following close behind, would slam into the enemy.

All of this required extensive training and practice.  This was accomplished by creating a ‘Large Standing Professional Army’ rather then relying on conscripted spear levies, short term militia drafts, hastily hired mercenaries and a small core of full time men at arms.  That of course required money.  The financial reforms that the Emperor initiated were just as important to his military success as his tactical reforms.