On 12 June Berwick was killed by a cannonball while inspecting the trenches, and command of the besiegers fell to Marshals d'Asfeld and Noailles.

Whilst a body double ostensibly left Brest by sea, Stanislas crossed Germany incognito and arrived at Warsaw on 8 September.

Louis XV's courtiers (including the princes of Conti and Eu, the counts of Clermont, Charolais and Belle-Isle, the duc de Richelieu, but also Maurice de Saxe, Augustus III's half-brother and the former lover of Anna Ivanovna, now the tsarina of Russia) joined up under marshal James FitzJames, Duke of Berwick to form an army for invading the Rhineland with the objectives of gaining the Duchy of Lorraine and distracting Austria from events in Poland.

Although they captured and occupied the fortress, most of the army was withdrawn to the west bank of the Rhine due to the onset of winter in December.

During the winter, Austrian field marshal Prince Eugene of Savoy began gathering forces of the empire at a camp near Heilbronn to oppose the French.

On 19 June Eugene, under orders from the Kaiser, began moving his army, which had since grown to over 70,000 men, toward Philippsburg with the goal of relieving the siege.

D'Asfeld responded by building additional boat-bridges over the Rhine to speed the movement of cavalry across the river, and redirected some of the siege personnel to face Eugene's threat.