Now this foreknowledge cannot be elicited from spirits;
it cannot be obtained inductively from experience, nor by any deductive calculation.
Knowledge of the enemy's dispositions can only be obtained from other men. - Sun Tzu
If Sun Tzu, a 7Century BC General did not rely on Divinations or Magic, there is something to be said about the eternal nature of his wisdom. Especially when in many other quotes, he can be attributed a empiricist.
Scouts must be chosen who are stead, keen-eyed, reliable, serious and fonder of their reputation than of money; such men make accurate reports. - Strategikon.
Spies should be very bold and move right in among the enemy, so they may be regarded as belonging to the same race. The men making patrols should be reliable; they should look very manly and be a cut above the other soldiers in physical appearance, morale and equipment, so they may project a noble image in confronting the enemy and if captured make a good impression on them. -Spying on the Enemy, Capture of Scouts or Spies trying to Hide in our Army the Strategikon.
Fighter > Soldier (which can be Archer or Heavy Infantryman)
Barbarian > Medium Infantry, Kurasores or Assault/Storm Troops. these guys are meant to move quickly as to flank or shock the opposition.
Consider all the other Spellcasting Classes are powerful courtiers that rely on social resources and moral cause (Cleric), organization (Wizard), or charisma (Sorcerer) to achieve great feats.