The Kendra Valley Massacre was an event during the Cardassian Occupation of Bajor in which the Cardassians ambushed and killed 43 members of the Bajoran Resistance in the Kendra Valley on Bajor after the location of their encampment was revealed by a Bajoran collaborator. This collaborator was thought to be Prylar Bek, who hanged himself shortly afterwards aboard Terok Nor. However, the information was actually revealed by Kai Opaka, who knew that the Cardassians would have wiped out every village in the valley to eliminate the resistance. Therefore, she sacrificed the lives of the resistance fighters, including that of her son, to save the lives of about 1,200 other Bajorans in the valley.
Years later in 2370, Vedek Winn Adami learned evidence from collaborator Kubus Oak implicating Vedek Bareil Antos in the massacre. Bareil dropped out of the race for kai so that the information would not be publicized, in order to protect Kai Opaka's memory. (DS9: "The Collaborator")