"Take no thought," said Augustine, "for long voyages; go where your faith is; it is not by ship, but by love, that we go to Him who is everywhere." Events soon rendered the pilgrimage to Jerusalem difficult, and for some time impossible.

At the commencement of the seventh century, the Greek empire was at war with the sovereigns of Persia, successors of Cyrus and chiefs of the religion of Zoroaster.

One of them, Khosroes II., invaded Judea, took Jerusalem, led away captive the inhabitants, together with their patriarch, Zacharias, and even carried off to Persia the precious relic which was regarded as the wood of the true cross, and which had been discovered, nearly three centuries before, by the Empress Helena, whilst excavations were making on Calvary for the erection of the church of the Holy Sepulchre.

But fourteen years later, after several victories over the Persians, the Greek emperor, Heraclius, retook Jerusalem, and re-entered Constantinople in triumph with the coffer containing the sacred relic.

He next year (in 629) carried it back to Jerusalem, and bore it upon his own shoulders to the top of Calvary; and on this occasion was instituted the Feast of the Exaltation of the Holy Cross.
Great was the joy in Christendom; and the pilgrimages to Jerusalem resumed their course.
But precisely at this epoch there appeared an enemy far more formidable for the Christians than the sectaries of Zoroaster.