In the north, the Austrian siege of Lille had completely failed by 8 October, and Dumouriez now resumed his interrupted scheme for the invasion of the Southern Netherlands. He took commanded of the newly formed Armée de la Belgique – comprising 40,000 soldiers from the Valmy campaign – at Valenciennes on 20 October. Controlling enormously superior forces, ten days later he made his advance to Mons, late in the season and surprising the Austrians. On 6 November, he won the first great victory of the war at Jemappes near Mons and, this time advancing boldly, he overran the whole country from Namur to Antwerp within a month. He began planning the invasion of the Dutch Republic.