Ernst Christoph von Nassau descended from a Silesian family in Hartmannsdorf near Glogau.

[2] After the death of his wife, Ernst Christoph lived with the widow of an officer of his regiment, Maria Elisabeth Biebisch, with whom he had three children: Anna Francisca Caroline, Georg Ernst Christoph (born 1747) and Friedrich Joseph Alexander (born 1748/49).

Soon Nassau's talents were recognized and he became lieutenant colonel of the cavalry and general and governor-general of Dresden, where he was assigned to Count and Field Marshal August Christoph Graf von Wackerbarth (1662–1734).

After the death of August II in 1738, Nassau and the ministers Brühl and Sułkowski disputed the future of the Saxon army.

Although no horses were available, the regiment was ordered into the camp near Strehlen, where it came under the command of Kurt Christoph Graf von Schwerin.

In late 1744, upon his promotion to lieutenant general, he received a corps of 8,000 to 10,000 men, with whom he was to secure the Silesian countryside and occupy the fortifications.

He also occupied a line of towns in Silesia: Patschkau, Neustadt, Klein Glogau, Löbschütz, Jägerndorf, Troppau and Oderberg.

After the Prussians had to withdraw from Prague under the General Gottfried Emanuel von Einsiedel, Nassau was to occupy Kolín first and thus secure the supply chain for the main army and, later, join Frederick at Marklissa, near Breslau.

[2] On 5 March 1746, he was elevated to the rank of a Prussian count and he received a golden tabloid from Frederick with a personal acknowledgement.

[2] He maintained a diary of his experience during the Second Silisian War, which was published as Beitrag zur Geschichte des zweiten Schlesischen Krieges in 1780.