NINGBO, China — With China stumping assertively on the world stage, one might think Beijing would be open, even gracious, about the country’s past. To the contrary, history remains an exceedingly sensitive subject here, drawing relentless attention from authorities anxious to keep all skeletons safely in closets.

As a university professor in China, I face the consequences of this official apprehension every day. My young, bright students know little about their country’s recent past. What they do know tends to agree with government-sponsored discourse on the pride and glory of China’s rise after a century of humiliation by Western powers. Library and bookstore shelves tell, with enviable conviction, this same story of national grandeur. And it is hard to get around that government-approved tale. Some of us at the University of Nottingham at Ningbo recently attempted to order a standard Western work on China’s history, Jonathan Spence’s The Search for Modern China. Our efforts ran aground when customs officials refused to allow the book shipment into the country. The agent courteously proposed to manually cut out the censored sections — including photos of the Tiananmen Square massacre and Spence’s account of the Cultural Revolution — to get the customs clearance. These are things the Chinese people are not supposed to know.

Historians of China face secrecy and restrictions everywhere as the key archives remain largely inaccessible, even though the Chinese archives law provides for the opening of official documents to the public after 30 years. Some progress has been made with declassification, notably at the Chinese Foreign Ministry, to appease international scholars. Academics can now read, though not print, digitized memos and telegrams from 1949 through 1965. Still, even these documents have been pre-selected to avoid potential embarrassment for the government. The party archives, which host the records of the Communist Party’s holy of holies — the Politburo — are closed. Anyone in China interested in studying the origins of the Korean War, which took place more than 60 years ago, will not get very far. The Great Leap Forward? The Cultural Revolution? Same story. Uncomfortable episodes of China’s recent history have become a subject of official amnesia and a victim of the government’s monopoly on truth.

Consider the case of Lin Biao, a hero of the Chinese Civil War, and later Mao Zedong’s comrade in arms during the Cultural Revolution, who died in 1971. Lin, who is well remembered for his appearances atop Tiananmen Square, the Little Red Book in his hand, supposedly conspired to kill the Chinese leader, even though he was Mao’s anointed successor. When the plot was discovered, he fled to the Soviet Union, then China’s archenemy, but he never made it: His plane crashed in Mongolia after allegedly running out of fuel.

This is the official story; this is as much as the Chinese government is willing to say 40 years on. We do not know whether Lin Biao really planned to kill Mao. Their fallout could have been a personal feud or, as the chairman later claimed, a policy disagreement (Lin Biao is said to have opposed the Sino-American opening).

In 2003, the crash report, including grisly photos of burned victims, was leaked from Mongolian intelligence archives. Contrary to the official Chinese explanation, the report (which was made available to me) showed that the plane had plenty of fuel when it crashed. No attempt had been made to land the plane, and weather conditions were fine. Mongolian investigators concluded that the pilot made an error. But they had no access to the plane’s black box; the Soviet military took it, along with one of the plane engines. The Soviets later came back and took the heads of the two victims with golden teeth, which, it turned out, belonged to Lin Biao and his wife.