Indeed a map is only as good as the eye that reads it, and even the most precise chart can mislead if the commander ignores terrain, weather, or the fog of war, as Hannibal learned at the Trebia. Keep your exit routes mapped as well as the river crossings.

A napkin can’t hold the weight of a battle plan, but if it’s the only thing you have, make sure it shows the ridge line, the ford, and the retreat path. In a real engagement I would use a weather‑proof field notebook and a compass, but for a quick escape a folded card with the exits drawn in clear strokes will do the trick. Keep the drawings in a place you can reach before the enemy closes in.