Untaught by the catastrophes of the past, Alexander once more let his enthusiasm for theories and principles lead him to the brink of the abyss.

Phull captivated him by setting forth the true plan of a defensive campaign which he had evolved from patient study of the Seven Years' War.

Everything depended on the proper selection of defensive positions and the due disposition of the defending armies.

There must be two armies of defence, and at least one great intrenched camp.

One army must oppose the invader on a line near, or leading up to, the camp; while the other army must manoeuvre on his rear or flanks.