Meanwhile, Brunswick had left Landres on 18 September, passed the northern defiles and then swung round to cut off Dumouriez from Châlons. He himself wanted to fight Dumouriez at Sainte-Menehould, but Prussian king Frederick William II, misled by false news that Dumouriez was withdrawing to Paris, ordered Brunswick to cut the retreat. At the moment when the Prussian manoeuvre was nearly completed, Kellermann, commanding in Dumouriez's momentary absence, advanced his left wing and took up a position between Sainte-Menehould and Valmy. The result was the Cannonade of Valmy (20 September 1792). Kellermann's infantry, nearly all regulars, stood steady. The French artillery justified its reputation as the best in Europe, and eventually, with no more than a half-hearted infantry attack, the duke broke off the action and retired.