TVXQ became a duo starting in 2009, continuing with U-Know Yunho and Max Changmin. The group had originally debuted under SM Entertainment as a five-member act in 2003.
In July 2009, members Jaejoong, Yoochun, and Junsu filed a legal action against SM Entertainment over their exclusive contracts. A Seoul court granted the three members a temporary injunction in October, which halted TVXQ's group activities in South Korea and led to the group's split.
The departing members later formed JYJ, while Yunho and Changmin continued promoting under the TVXQ name. Their first major return as a duo came with the 2011 Korean album Keep Your Head Down.
The group is also known as DBSK or Dong Bang Shin Ki, names based on different romanizations of its Korean name. TVXQ's transition from five members to two became one of K-pop's most discussed lineup changes.