Dong and his partners also published the Ming Dynasty Great Wall Inspection Report. The book compiled their observations and thoughts about walking along the bulwark barefoot and is the first of its kind.

But rather than offering closure, completing this quest inspired Dong to tackle new aspirations.

He began to study in Peking University's history and geography departments. Over the next three decades, he made more than 150 field trips to the wall and published about a dozen academic papers in scholarly journals.

China Great Wall Museum deputy editor-in-chief Zheng Yan joined the China Great Wall Association after hearing about Dong's story and reading the Ming Dynasty Great Wall Inspection Report. He believes Dong's work is invaluable.

"I've seen many Great Wall researchers whom I call 'sofa scholars'," he says.

"They do research by sitting and reading. Dong is one of the few 'walking researchers'. And he's among the few to study the wall's entirety. I think he lives for it."

Dong Yaohui announces the start of a campaign for young volunteers to preserve the Great Wall at Shanhaiguan, the easternmost pass. Provided to China Daily

Dong says a mission to protect the wall had eclipsed his scholarly ambitions until recently.

He organized a 45-day media trip to 101 Great Wall sites in eight provinces in 2002. The findings were shocking. The wall's total length, including complete and crumbling stretches, is no longer than 2,500 km. Human activity, including infrastructure construction and poor renovations, have inflicted tremendous damage.

In 2005, he initiated a campaign to engage the whole world in the task of repairing the graffiti along the entire wall. He also brought government officials to cities along the wall to learn preservation methods from foreign counterparts.

Dong was the only scholar who stood up and criticized the proposed Regulations for the Protection of the Great Wall, during the law's formulation, in 2006, as being too vague.

The China Great Wall Association's deputy secretary-general Zhang Ji says: "People always talk about the 'Great Wall spirit'. But you'll never know what that spirit actually is until you meet Dong. He embodies its true meaning - tenacity and persistence."

Dong believes that, as long as he's working for the wall's benefit, even his critics will appreciate his effort.

In 2008, the Cultural Relic Press under the State Administration of Cultural Heritage published a collection of Dong's articles, including some of his harsh criticisms. Dong sees it as a signal that the government is starting to appreciate his views.

He says he is delighted to discover that the government and society have recently increased financial investments and advanced policy initiatives to protect the relic.

This has freed him up from his preservation advocacy work to write the China Great Wall Chronicles, he says.

"I think it's time to present the comprehensive results of our Great Wall studies completed over the past 30 years, so young researches can go much further by starting from where we've left off," he says.

Contact the writer at hanbingbin@chinadaily.com.cn.