During World War I, Kaupisch served on the General Staff and rose gradually in the ranks and in 1917 promoted to Major.

It was as head of this command that he April 9, 1940 led Operation Weserübung Süd, forcing the occupation of Denmark.

leaflets with a call to refrain from resistance which German planes dropped during the early morning were signed by Kaupisch.

Anticipating the imminent defeat of Germany, Kaupisch and his family left their home in Westend, Berlin and settled in Bad Berka, a spa town lying approximately 10 km south of Weimar.

That summer, he was also interviewed by a Danish journalist who noted that the retired General had adapted to the peacetime lifestyle.