The Philippines' anti-graft body filed criminal charges against former President Benigno Aquino on Wednesday for mishandling a botched anti-militant raid that resulted in the death of 44 police commandos in 2015.
The police officers' deaths at the hands of an overwhelming number of rebel gunmen contributed to the stalling of peace efforts with Muslim separatists in the southern Philippines and was the biggest crisis of Aquino's 2010-2016 presidency.
The Office of the Ombudsman said it had charged Aquino with usurpation of authority, as well as graft and corruption, following preliminary investigations.
The agency said the former leader allowed a suspended police chief to be involved in the planning and execution of the January 2015 incident in Mamasapano in Maguindano province and kept the interior minister and police officer in charge out of the loop.
Aquino's representative did not respond immediately to a request for comment.
Police Special Action Force commandos killed two al Qaeda-linked militants but were ambushed and outnumbered by militants during the raid.
The incident caused national outrage and Aquino's approval and trust ratings fell to record lows.
A bill put to Congress by the government and the separatist Moro Islamic Liberation Front to grant self-rule over the predominantly Muslim region of Mindanao island stalled, which many in the process blamed on the impact of the Mamasapano incident.
The bill has since been reworked and is expected to be put to Congress again soon, with President Rodrigo Duterte determined to see it passed as a means to develop the country's most impoverished region and arrest the spread of radical sentiment and the influence of the Islamic State group.