During the next few years, subsequent to the Simla conference, Shere Ali, though he had received considerable assistance from us, both in money and arms, was not altogether satisfied, and one or two incidents occurred during that period which gave him umbrage. Lord Northbrook, the Viceroy in 1875, was not unaware of the somewhat cold and capricious spirit of the Ameer, but in writing to London he pointed out that Shere Ali's situation was difficult, not only from the risk of revolution at home, but also of attack from abroad, but that on the whole he was to be relied on. A change, however, was coming over the scene, and our policy reverted from conciliation to compulsion. It was a critical period in the history of frontier policy, and demands careful consideration. It must not be forgotten that although amongst those best qualified to judge the majority had long been opposed to advance and conquest in territories beyond our North-West frontier, and entertained but little fear of Russian aggressive power, still there were others--men of long experience, who had filled high positions in India--who held different views; and it is probable that not only successive British Governments, but the public generally, who have no time for carefully weighing the diverse aspects of the subject, were influenced sometimes one way, sometimes another. In the many difficulties connected with our world-wide Empire this must always be more or less the case. For instance, the late Sir H. Rawlinson, a few years before the second Afghan war, took a very alarmist view of the progress of Russia, not only in Central Asia but also in Asia Minor. He considered that her advance from Orenburg was only part of one great scheme of invasion; and he averred that the conquest of the Caucasus had given her such a strong position that there was no military or physical obstacle to the continuous march of Russia from the Araxes to the Indus. [Footnote: Parliamentary Papers, _Afghanistan_, 1878.] He described it as the unerring certainty of a law of nature. But, throughout, he ignores distances, blots out the mountains, deserts, and arid plains of Persia and Afghanistan, and takes no account of the warlike races who would bar the path. It requires a very large map to embrace all the details of this widespread strategy. Some account has already been given of the weakness, in a military point of view, of Russia in Central Asia, and of the distance of her scattered troops from the main resources of the Empire. But, in addition, it must be remembered that the mountains of Afghanistan also form a natural and enduring barrier against a further advance. The great Hindoo Koosh range, running all along the northern part of that country, forms indeed the real scientific frontier between the two Empires, the few passes over its snowy crests ranging from 12,000 to 18,000 feet high, and only open for a few months in the year.