His first posting in China was to the South Shanxi mission in 1894, serving there through the period of the Boxer Rebellion until his appointment as vicar apostolic of North Shandong in 1902, moving to Jinan and working with Italian missionaries based in the region.
[1] By the time of his appointment as titular Bishop of Paltus in 1902, he was said to preside in Jinan over 11 Franciscan friars, 18 native Chinese priests, 18,000 Catholics, 13,900 catechumens, and 134 churches or chapels.
[3] The work of Giesen and other Dutch missionaries, helped keep the German missions survive in Shandong during and in the aftermath of World War I.
[4] In the spring of 1900, as the Boxer Rebellion was unfolding across northern China, Ephrem Giesen was located at Xinzhuang, south of Machang, where a Catholic fortified stronghold had been established.
[5] Local Catholics managed to hold off Boxers in many cases, and there were no Dutch friars killed in the attacks in the region during the summer of 1900.