HTC now sues Apple. As it is known, in March this year, Apple sued HTC because the latter seemed to have violated (it is the legal term used in the summons) about 10 patents of the company from Cupertino.
At that time people from HTC were glad to say they will fight back. And they did it now, two months later. The process’s reason is about the same. Justification of the action is “protecting their own intellectual property.”