Nigeria has reinstated a general implicated in mass murder, underlining the government’s “monumental failure” to stamp out impunity for war crimes, Amnesty International said Monday. The London based rights group last year called for an investigation of nine senior commanders including Maj. Gen. Ahmadu Mohammed for possible criminal responsibility for war crimes including the deaths of more than 8,000 detainees since 2011. Mohammed was commanding officer when soldiers killed around 640 unarmed detainees after Boko Haram extremists attacked Giwa barracks in northeast Maiduguri city, according to Amnesty. President Muhammadu Buhari in June promised to investigate the allegations and deal with all alleged abuses by the military, but nothing has been done. Mohammed was retired in 2014 after mutinying soldiers shot at him, revolting because they said a dozen colleagues killed by Boko Haram in a night ambush on the road from Chibok had been unnecessarily sent into danger. The general was reinstated quietly in January, according to the military at his own request. “Young men and boys, rounded up by the military, were either shot, starved, suffocated or tortured to death and no one has yet been held to account,” Amnesty International said in a statement. “It is unthinkable that Maj. Gen. Mohammed could resume command of troops before an investigation has even begun. His reinstatement “makes mockery of commitments to end war crimes and underlines the monumental failure of the government to stamp out impunity for war crimes at the highest level.