MATSUE, Japan — Before Japan’s attack on Pearl Harbor, Emperor Hirohito criticized plans to go to war with the United States as “self-destructive” and opposed an alliance with Nazi Germany, though he did little to stop the war that Japan waged in his name, according to the long-awaited official history of his reign released on Tuesday.

The 12,000-page history of Hirohito, who was emperor from 1926 to 1989, including during World War II, also shows him exulting over the victories of his armies in China.

Despite its length and some new details, the report contains little that will surprise historians or challenge the established view that Hirohito had little say in Japan’s decision to go to war, according to the Japanese news media, which had first access to the report. It also confirms the dominant view that Hirohito was reluctant to go to war with the United States.

The most controversial aspect of the report appears to be the fact that it took the Imperial Household Agency almost a quarter of a century to release its official history of Hirohito, who died in 1989 at age 87. The agency, which manages the affairs of the imperial family, explained the delay by saying it took time to put together the 61-volume history from 3,152 documents and records, some of them never previously made public.