On 19 July 1870 he joined the 2nd (Emperor Francis) Regiment of Guards Grenadiers and fought with it in the Franco-Prussian War.

On 12 January 1871 Quast was promoted to Sekondeleutnant and received the Iron Cross 2nd Class.

In March 1913 Quast was named commanding general of the IX Corps in Altona, Hamburg.

Fighting in the Battle of Tirlemont (Hautem-Sainte-Marguerite), von Quast was promoted to General der Infanterie on 19 August 1914.

His stern defensive and his organizatorial skills were noticed and he received the Pour le Merite from the hand of Emperor Wilhelm II on 11 August.