What song was recorded by a group that debuted in 2012 with twelve members for their fourth studio album "The War"? 
Ko Ko Bop: "Ko Ko Bop" is a song recorded by South Korean boy band Exo for their fourth studio album "The War". Exo (band):  Formed by S.M. Entertainment in 2011, the group debuted in 2012 with twelve members separated into two subgroups, Exo-K (Suho, Baekhyun, Chanyeol, D.O., Kai, and Sehun) and Exo-M (Xiumin, Lay, Chen and former members Kris, Luhan and Tao ), performing music in Korean and Mandarin respectively.
"Ko Ko Bop"