From the mouth of the Amur, where Nikolayevsk is situated, to the southern shore of Korea there rests on the coast of eastern Asia an arch of islands having at its northern point Sakhalin and at its southern Tsushima, the keystone of the arch being the main island of Japan. This arch embraces the Sea of Japan and is washed on its convex side by the Pacific Ocean. Immediately after the transfer of Russia's naval base from Nikolayevsk to Vladivostok, an attempt was made to obtain possession of the southern point of the arch, namely, Tsushima. A Russian man-of-war proceeded thither and quietly began to establish a settlement, which would soon have constituted a title of ownership had not Great Britain interfered. The Russians saw that Vladivostok, acquired at the cost of so much toil, would be comparatively useless unless from the sea on whose shore it was situated an avenue to the Pacific could be opened, and they therefore tried to obtain command of the Tsushima channel. Immediately after reaching the mouth of the Amur the same instinct had led them to begin the colonization of Sakhalin. The axis of this long narrow island is inclined at a very acute angle to the Usuri region, which its northern extremity almost touches, while its southern is separated from Yezo by the strait of La Pérouse. But in Sakhalin the Russians found Japanese subjects. In fact the island was a part of the Japanese empire. Resorting, however, to the Usuri fiction of joint occupation, they succeeded by 1875 in transferring the whole of Sakhalin to Russia's dominion. Further encroachments upon Japanese territory could not be lightly essayed, and the Russians held their hands. They had been trebly checked: checked in trying to push southward along the coast of the mainland; checked in trying to secure an avenue from Vladivostok to the Pacific; and checked in their search for an ice-free port, which definition Vladivostok did not fulfil. Enterprise in the direction of Korea seemed to be the only hope of saving the maritime results of the great Trans-Asian march. Was Korea within safe range of such enterprises? Everything seemed to answer in the affirmative. Korea had all the qualifications desired by an aggressor. Her people were unprogressive, her resources undeveloped, her self-defensive capacities insignificant, her government corrupt. But she was a tributary of China, and China had begun to show some tenacity in protecting the integrity of her buffer states. Besides, Japan was understood to have pretensions with regard to Korea. On the whole, therefore, the problem of carrying to full fruition the work of Muravief and his lieutenants demanded strength greater than Russia could exercise without some line of communications supplementing the Amur waterway and the long ocean route. Therefore she set about the construction of a railway across Asia.