The 10th Corps, having swept the right bank of the Niemen, concentrated on Rossieni, whence it set out on July 8th for Riga, Grawert advancing directly on the port by way of Mitau, while Grandjean’s division, accompanied by Macdonald, moved on the right. Before the 30,000 or 32,000 men of the 10th Corps the Russian detachments in Kurland were helpless, and fell back at all points into Riga. By the 18th the invading forces were ranged along the Aa river, which passes by Mitau, the capital of Kurland, and, flowing nearly parallel to the Düna, enters the Baltic some 20 miles west of Dünamunde. Mitau, Bausk, and the other towns along the Aa were occupied, and the Prussians reached out with their left to the sea. Essen could form for field operations only a force of 8 depôt battalions, 8 squadrons, a battery and some Cossacks--4500 men at most, with 10 guns--which he sent under Lieutenant-General Lewis towards Bausk. Lewis was too late to defend Mitau or Bausk, and took up a defensive position at Eckau between the latter place and Riga. Against him Grawert advanced on July 19th with 7 battalions, 4 squadrons and 4 batteries--5000 men and 32 guns. Lewis was beaten with a loss of over 600 prisoners besides killed and wounded, and driven back upon Riga. The Prussians moved up nearer to the city, and Essen, on July 22nd, losing his head, ordered the suburbs to be fired. There was absolutely no need for this reckless step. Macdonald had not a siege gun within reach. The misery and destitution occasioned were, of course, terrible; the mere immediate material loss is said to have been valued at 15,000,000 paper rúbles (about £600,000). Macdonald, after Eckau, moved with Grandjean’s division towards Jakobstädt, and established his head-quarters there on the 22nd. His advance-guard of 4 Polish battalions, under Prince Radziwil, moved down the left bank of the Düna on Dünaburg. Radziwil occupied the place on the 30th and 31st, the garrison having been withdrawn by Wittgenstein, and on August 8th Macdonald arrived with the rest of Grandjean’s division. He blew up the half-finished fortifications, and destroyed all the artillery, ammunition and tools which he could not carry away. De Chambray blames him for this, saying that he should have retained them for the siege of Riga; he also criticises him for not crossing the Düna and striking at Wittgenstein’s communications. It seems, however, clear that Macdonald’s appointed task was the siege of Riga; and he obviously could not undertake independent operations without Napoleon’s order. His position, as he told Oudinot, was very difficult. His force was scattered over a wide extent of country, and in the absence of any proper staff he was burdened with petty details. [Illustration: MARSHAL OUDINOT, DUKE OF REGGIO Commander of the 2nd French Army Corps From the painting by Robert Lefèvre at Versailles]