A large French army under the command of the Duke of Berwick besieged and captured the fortress, which was lightly garrisoned and in poor condition.

Whilst a body double ostensibly left Brest by sea, Stanilas 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 to form an army for invading the Rhineland with the objective of distracting Austria from events in Poland and gaining the Duchy of Lorraine.

The village and fortress of Kehl was located near the Margraviate of Baden in the Holy Roman Empire, just across the Rhine River from the French city of Strasbourg.

The fortress at Kehl, and that at Philippsburg to the north, provided strategic military control over major crossings of the upper Rhine, which formed the boundary between French-controlled Alsace and the various principalities of the empire.

Nominally the responsibility of the emperor, maintenance and defense of the fortress belonged to the Swabian Circle, which was largely dominated by the Duchy of Württemberg.

When the war broke out, numerous works to repair and expand the fortress were underway, but key defenses near the Rhine were incomplete.

Control over the remainder of Lorraine was rapidly established, and the two commanders left garrisons throughout the duchy before sending the bulk of their forces into Alsace to focus on the campaign on the Rhine.

That siege was successfully concluded by his second in command, the marquis d'Asfeld, and marked the end of significant military operations in the Rhine valley for the war.