For about 100 miles south-westward from Grodno there was no natural frontier; thence to the Austrian border it was formed by the Bug, which, issuing from Galicia below the town of Sokal, flows northward for some 110 miles to Brest-Litovsk, and then north-westward for 70 miles more to what was in 1812 the Polish border. For nearly 100 miles near Brest-Litovsk the Pinsk Marshes close in upon the river. The Austro-Russian border need not be considered, for it was neutralised; Schwarzenberg operated only as an auxiliary, in Poland. Trade continued as usual, and when Admiral Chichagov’s army passed close along the frontier on its way to attack Schwarzenberg it was not molested by Russia’s nominal enemies. The first provinces on the right bank of the Niemen entered by the _Grand Armée_ were Courland to the north and the various districts which had once formed the Grand Duchy of Lithuania to the southward. Lithuania was and is a region of woods and marshy plain land, broken in places, and intersected in every direction by streams flowing in deeply sunken channels. In the south there stretched inland from the Bug the famous marshes of Pinsk, one of the largest tracts of fenland in the world, extending as it does for some 300 miles east and west, by over 100 north and south. The soil, even when not actually swampy, was generally soft, and there were hardly any good roads. Towns were few; the population was sparse and wretchedly poor. At distances varying from about 120 to over 300 miles eastward of the Bug and Niemen a second natural line is formed by the Düna and the Dnieper. The Düna rises near the Volga, flows roughly south-west to Vitebsk, there turns west-north-west and runs for nearly 300 miles to the Baltic at Riga. Above Vitebsk it is fairly often fordable during the summer heats. In 1812 it was bridged at Vitebsk and Dünaburg, half-way to Riga, but, since the left bank is generally higher than the right between these places, the river does not afford a good line of defence. From the Düna at Vitebsk southward to the Dnieper at Orsha is a gap of about 45 miles. At Orsha the Dnieper, one of the great rivers of Europe, turns to the southward, to flow for 800 miles into the Black Sea. Seventy miles above Orsha is Smolensk, where in 1812 there was a bridge. At Mohilev, 50 miles below Orsha, there was another. The river is rarely fordable even during the summer. Its tributary the Berezina, which was a most important strategic feature in the campaign, flows towards it on the east at an acute angle for 200 miles, joining at a point nearly due east of Warsaw and west of Orel. In 1812 there were bridges at Borisov and Bobruisk, but in general the river is fordable in summer. The right bank is usually higher than the left.