Kuentz was born in Ranspach, Alsace, the son of a railwayman,[2] and was conscripted by the Kaiser's army at the age of 19, since Alsace-Lorraine and its Franco-German ethnic population had been under German authority since 1871, following the French defeat in the Franco-Prussian War.
While serving in the Imperial German Army during World War I, he saw action on both the Eastern and Western Fronts.
In November 2004, he met British veteran Harry Patch, who had fought on the opposing side of him in the Battle of Passchendaele.
In that same year, Kuentz gave a series of thirty interviews, the purpose of which was to share his recollections of The Great War.
At the time of his death, Kuentz was (although incorrectly) believed to have been the Imperial German Army's (and indeed all of Germany's) last surviving veteran of The Great War.