The M23 rebellion is staffed largely by ex-CNDP officers who mutinied starting early April, demanding the implementation of the March 23, 2009 agreement with the government. That deal brokered their integration into the national army, and the officers say that many of its aspects - including the confirmation of their ranks, adequate salaries, political positions of their cadres - were not respected, and that they were discriminated against.
So how many have defected?
Here are two tables that go some way to addressing this question, although further research is needed.
First, a table of the CNDP structure in 2008, just before integration. I have provided their ranks just before the M23, and tried to list most of their senior officers (feel free to submit other names). In red are members who have defected to the M23. As one can see, they constitute about half of the senior ex-CNDP officers.