Perozes persuaded himself that he would sufficiently observe his engagement if he kept its letter; and accordingly he lowered the pillar, and placed it upon a number of cars, which were attached together and drawn by a train of fifty elephants, in front of his army.
Thus, however deeply he invaded the Ephthalite country, he never "passed beyond" the pillar which he had sworn not to pass.

In his own judgment he kept his vow, but not in that of his natural advisers.

It is satisfactory to find that the Zoroastrian priesthood, speaking by the mouth of the chief Mobed, disclaimed and exposed the fallacy of this wretched casuistry.
The Ephthalite monarch, on learning the intention of Perozes, prepared to meet his attack by stratagem.

He had taken up his position in the plain near Balkh, and had there established his camp, resolved to await the coming of the enemy.

During the interval he proceeded to dig a deep and broad trench in front of his whole position, leaving only a space of some twenty or thirty yards, midway in the work, untouched.