Those who have served in/or with the infantry knows that your zip and their zag can but one or both of you in a body bag. The First Law of Warfare is Murphy's Law; what can go wrong will, at the worst possible time and the worst possible place. Good training, equipment and leadership is validated by successful evasion, neutralization, and changing plans at the right time.
In addition to Handy Terrain Analyses, the hands on tool to determine the Roles and Rules by which all cultures in the Area of Interest, and the analyses of the drama that is central to a group's survival. It is METT-TC with the C being Culture. I don't mean knowing whether to kiss, bow or shake thier hands. Culture shows up in how they used the ground before the troops arrived, and gives a clue to everyone's "tipping point". In the time of the Crusades, the culture of the cavalry was to chase after the enemy's cavalry, only to return to see the infantry face down for next dozen miles.
Task organization and battle drill focused on the specific MOS(Military Occupational Specialty) and home zipcode. The MOS's pf a medieval formation is no less complicated than today's.