 Complete the following phrase:  Frankfurt was ordered under the contract name Ersatz  and was laid down at the Kaiserliche Werft shipyard in Kiel in 1913 and launched on 20 March 1915. The ships was commissioned into the High Seas Fleet on 20 August 1915. Frankfurt saw extensive action with the High Seas Fleet during World War I. She served primarily in the North Sea, and participated in the 