The late Emperor Hirohito privately expressed regret about atrocities committed by Japanese troops in the Chinese city of Nanjing in 1937, saying he hadn’t fully known what the army was doing but wished he could have stopped it, according to newly released records.

Notes of Hirohito’s remarks in the early years after World War II show the emperor mostly blamed the war on military officers he believed drove Japan into a conflict it couldn’t win. But the documents also show the emperor felt pained about his own role and tried unsuccessfully to give a public speech in 1952 laying out his remorse. The notes, taken by former Imperial Household Agency chief Michiji Tajima, were released Monday by public broadcaster NHK, which aired a documentary on the subject Saturday.

Historians still debate the war responsibility of Hirohito, who reigned from 1926 until his death in 1989. Until Japan’s defeat in World War II, he was treated as a deity and was the formal head of Japan’s armed forces.

Some historians view him as essentially a figurehead who could do little to stop military officers bent on building a Japanese empire in East Asia. Others highlight Hirohito’s hands-on role in military planning, including his personal authorization of the attack on Pearl Harbor in December 1941. In his 2001 biography of Hirohito, historian Herbert Bix wrote that while the Nanjing massacre was unplanned, Hirohito knew of and approved annihilation campaigns in China that included burning villages thought to harbor guerrillas.