▁s ank ▁accident ally . ▁R ais ed ▁in ▁ 1 9 2 1 , ▁she ▁too ▁was ▁broken ▁up . ▁ ▁B ism ar ck ▁class ▁ ▁In cre ased ▁dem ands ▁on ▁the ▁fleet ▁to ▁protect ▁German ▁over se as ▁economic ▁interests ▁in ▁the ▁w ake ▁of ▁the ▁Franco - Pr uss ian ▁War ▁necess itated ▁the ▁construction ▁of ▁new ▁cor v ettes ▁to ▁shoulder ▁the ▁bur den . ▁In ▁addition , ▁by ▁that ▁time ▁the ▁vessels ▁that ▁had ▁been ▁acquired ▁under ▁the ▁initial ▁fleet ▁plans ▁had ▁become ▁worn ▁out , ▁making ▁the ▁ac quisition ▁of ▁new ▁vessels ▁even ▁more ▁important . ▁The ▁B ism ar ck - class ▁cor v ettes ▁were ▁based ▁on ▁the ▁Leipzig ▁design , ▁but ▁they ▁were ▁significantly ▁scale d ▁down . ▁They ▁had ▁a ▁disp lacement ▁of ▁more ▁than ▁a ▁thousand ▁tons ▁less ▁than ▁the ▁earlier ▁vessels , ▁carrying ▁a ▁l ighter ▁arm ament ▁and ▁less ▁powerful ▁engines . ▁Since ▁steam ▁engines ▁were ▁still ▁not ▁reliable ▁enough ▁to ▁be ▁the ▁only ▁source ▁of ▁mot ive ▁power , ▁full ▁ship ▁rig s ▁were ▁retained . ▁ ▁The ▁ships ▁of ▁the ▁B ism ar ck ▁class ▁served ▁in ▁a ▁variety ▁of ▁roles ▁throughout ▁their ▁care ers . ▁Bl ü cher ▁was ▁converted ▁into ▁a ▁tor ped o ▁testing ▁and ▁training ▁ship ▁shortly ▁after ▁her ▁completion , ▁and ▁she ▁was ▁used ▁to ▁help ▁develop ▁tact ical ▁doctrine ▁and ▁train ▁officers ▁and ▁sail ors ▁in ▁the ▁use ▁of ▁tor ped o es ▁until ▁she ▁was ▁badly ▁dam aged ▁by