His riding talents became clear at a young age, but he could not display them internationally until after World War II.

[1] At the 1952 Olympics in Helsinki, Thiedemann won medals in two equestrian disciplines, a feat since unequalled.

He placed third in the dressage team event, and won another bronze medal in the individual jumping contest with his favourite horse Meteor, with which he would win all major prizes in his career.

Thiedemann was the flag-bearer of the United Team of Germany (composed of both East and West German athletes) at the 1960 Olympics in Rome.

The United Team of Germany successfully defended their jumping title, Thiedemann winning his fourth Olympic medal.