He joined the military in 1870 and participated in the Franco-Prussian War where he received the Iron Cross (2nd Class).

[1] Von Zwehl was brought out of his retirement when World War I began and was assigned to lead the VII Reserve Corps, which was part of the 2nd Army.

He received the French surrender and was awarded with the prestigious Pour le Mérite on 8 September 1914.

[2] In September 1915 his corps was transferred to the 5th Army and was deployed in the Battle of Verdun.

It suffered serious losses throughout the year-long campaign, and von Zwehl was released from command in December.