The Crown Prosecution Service said two suspects under investigation following the death of three soldiers during a training exercise in Brecon Beacons last July will not face charges of gross negligence manslaughter.
Head of CPS Wales Catrin Evans said there was not enough evidence to establish the offence.
"There is insufficient evidence to support charges of gross negligence manslaughter against the two suspects.
“To establish an offence, (...) the prosecution would have to show that the suspects owed a duty of care to the victims, that this duty was breached, that this breach was an operative cause of death and that the conduct of the suspects was so negligent that it ought to be characterised as a crime.
Ms Evans stressed that the criminal investigation into the incidents would continue, with responsibility passing to the Health and Safety Executive.