W. D. Bird, Some Principles of Frontier Mountain Warfare
“ But when the line of march leads along a single file track, winding through narrow valleys, and over rugged mountains, when the column, compared to its strength, occupies an inordinate length of roadway, and is therefore especially vulnerable to flank attack, and when the enemy, or at any rate a portion of his warriors, prefer plunder of baggage to pitched battles, other measures to safeguard the force must be taken. ”
