[1] Born in Hartenholm, Schleswig-Holstein in wartime Germany, Tiedemann left school as a teenager.

After his retirement, he maintained a post as Professorial Research Associate at SOAS and as Professor of Chinese History, Shandong University, Jinan.

[2][3] His research mainly concerned the history of Christianity in China, with a particular focus on Shandong and the Boxer Rebellion.

He also edited the second volume of the Handbook of Christianity in China,[4] which totalled over a thousand pages; about half of the entries he wrote himself.

[6] A festschrift was published in honor of Tiedemann, edited by two of his former students, entitled The Church as Safe Haven (2018).