The mercenaries that landed in Terengaria (the Three Kingdoms) from across the Sea of Storms were mostly footmen, roughly 80% of their force, armed with a variety of weapons, including bows, spears, swords, but only a small portion had any armour of significance. The remaining 20% consisted of horsemen and archers. The archers were using relatively small bows, not the larger, more effective weapons that we would today refer to as Longbows. Their cavalry at that time was used for little more than skirmishing and scouting. The dominant force on the battlefield was the shield wall, so all of the mercenary footmen companies were skilled in its use.
The main tactic in the early days was to form the infantry in a solid line, with the archers on the flanks. Horses would generally be held in reserve until an opportunity for pursuit arrived. This led to many stagnant battles, with little room to manoeuvre. However, over the intervening years, as armour and weapons improved, cavalry became more dominant on the battlefield, and leaders began experimenting with new tactics.
The first Mercerian Chargers were bred in the early 600’s, but it wasn't until 839 that calvary became so effective on the battlefield. Until that time, the horsemen of the realm were considered a valuable part of the army, but still a role fulfilled by commoners. The introduction of expesive heavy armour changed all that, making it the domain of the rich, and the position of the knight was created. Knights came under the exclusive command of the king after the Farmers Rebellion in 893 MC, when their true potential was realized.
Up until the ascension of Queen Anna, the typical deployment of a Mercerian army mirrored tactics that had been deployed for centuries; footmen in the middle, with archers on one or both flanks, and using the knights, who counted on shock and awe to smash through enemy lines.
It is worth noting here that the armies of Norland are less disciplined than those of Merceria, so these tactics have proven quite effective over the years. Weldwyn, on the other hand, has well-trained troops of their own, to the effect that neither side could deal their enemy a crushing blow in past encounters.
These tactics have remained in effect until the development of new ideas under Gerald Matheson, who was appointed Marshal of the Realm when Queen Anna took the throne.