 Of the three ships in its class , only Derfflinger was ordered as an addition to the fleet , under the provisional name " K " . The other two ships were to intended to replace obsolete vessels ; Lützow was ordered as Ersatz <unk> Augusta for the elderly protected cruiser <unk> Augusta and the contract for Hindenburg was issued under the provisional name Ersatz <unk> , to replace the protected cruiser <unk> . 
