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Rh back upon Afghanistan as our defensible barrier. It followed that, as England receded, Russia pressed on, occupied the diplomatic ground that we had vacated, and converted the Persian power into an instrument for the furtherance of her own interests, which were not ours.

As Persia had just ceded to Russia some districts in the northwest, she was encouraged, by way of compensation, to revive a long-standing claim upon territory belonging to Afghanistan across her northeastern borders. In 1837, therefore, the Shah of Persia, who claimed Western Afghanistan as belonging of right to his crown, was preparing for an attack upon Herat, the chief frontier city of the Afghans on that side, and the key to all routes leading from Persia into India. Some of the leading Afghan Sirdars were in correspondence with the Persian king; and Shah Shuja', the hereditary prince, who had been driven out by a new Afghan dynasty, was an exile in the Pan jab, whence he made unsuccessful attempts to recover his throne, soliciting aid both from the Sikhs and the English.

Shah Shuja' represented the legitimate line of descent from Ahmad Shah Abdali, who had created the Afghan kingdom, but a few years before this time his family had been supplanted by the sons of a powerful minister. This is a well-known form of dynastic changes in Asia, produced by the natural tendency of rulership to fall out of the hands of those who cannot keep it into the grasp of those who can. It will be remembered that the royal house of the Maratha empire