The frontier was continually shifting, and Thutmosis III., like Thutmosis I., vainly endeavoured to give it a fixed character by erecting stelas along the banks of the Euphrates, at those points where he contended it had run formerly. While Kharu and Phoenicia were completely in the hands of the conqueror, his suzerainty became more uncertain as it extended northwards in the direction of the Taurus. Beyond Qodshu, it could only be maintained by means of constant supervision, and in Naharaim its duration was coextensive with the sojourn of the conqueror in the locality during his campaign, for it vanished of itself as soon as he had set out on his return to Africa. It will be thus seen that, on the continent of Asia, Egypt possessed a nucleus of territories, so far securely under her rule that they might be actually reckoned as provinces; beyond this immediate domain there was a zone of waning influence, whose area varied with each reign, and even under one king depended largely on the activity which he personally displayed. This was always the case when the rulers of Egypt attempted to carry their supremacy beyond the isthmus; whether under the Ptolemies or the native kings, the distance to which her influence extended was always practically the same, and the teaching of history enables us to note its limits on the map with relative accuracy.* * The development of the Egyptian navy enabled the Ptolemies to exercise authority over the coasts of Asia Minor and of Thrace, but this extension of their power beyond the indicated limits only hastened the exhaustion of their empire. This instance, like that of Mehemet Ali, thus confirms the position taken up in the text.