The second campaign, which the PLA said was the largest in world military history, was conducted between 1997 and 1999 on the border in two southwestern autonomous regions of Yunnan and Guangxi.

With experience and an unspecified increase in spending, better results were obtained, the local military area command said.

More than 500,000 landmines and 180,000 explosives were unearthed. At the Sino-Vietnam War's main battlefield, the smell of thousands of hectares of tea plants grown after 1999 replaced the previous choking smoke caused by exploded mines.

Mine removal has paved the way for prosperous border trade. China has been Vietnam's largest trade partner for more than two years, with trade hitting 16.6 billion U.S. dollars in the first 10 months of this year, surpassing the total 2007 figure, according to the Chinese government. Leaders of the two countries have set a target of US$25 billion by 2010, it said.

They also pledged to speed the creation of sub-regional economic areas, including a China-ASEAN (the Association of Southeast Asian Nations) free trade zone and trade corridors along the Mekong River, which originates in China, runs through Myanmar, Laos, Thailand, Cambodia and Vietnam and empties into the South China Sea.

"A peaceful border is part of any promising relationship between two armies and two countries and provides opportunities for increasing mutual respect and trust," said Jiang Yi, research fellow with the Chinese Academy of Social Sciences.

However, the danger of landmines has not been completely eliminated. It was estimated there were about 40 sq km of mined fields after two previous de-mining missions, with more than 500,000 mines and explosives remaining.

Complicated mix

Sun said one difficulty in the de-mining process was the large variety of mines, which could be set off in many ways. Nobody really knew how many types of mines were left behind by conflicts, but mixed mine-fields were really a headache for engineering troops.

The main type was the pressure mine, which could be found using metal detectors. Other types included mines made of plastics or liquids, which the metal detectors could not handle.

Another difficulty, he said, was that some mines had been buried for as long as three decades. They have rusted and "easily go off with a simple touch," he said.

The complicated geography of the border area, with uninterrupted tropical forests and mountains, made mine-clearing highly dangerous, he added. "After a downpour, some mines might be swept to the roadside, and others might be buried more deeply underground."

Fu said it's very dangerous work. Often, when one bomb was extracted from the upper layer of soil, soldiers found more than one layer of mines.

He recalled he broke into a cold sweat when his team found scores of layers of mines during a mission. "It's frightening," he said. They later found these mines accumulated after being swept to the site by rain and obstructed by rocks.

Such life-or-death situations have occurred many times during China's efforts to clear landmines along its border with Vietnam.

Fu and Sun could not remember how often they had stomped on newly de-mined areas to make sure the areas were truly safe.

Many of the mined areas were on mountainous slopes, which could not be reached by road, so the dynamite required to de-mine them was delivered on soldiers' backs. Sometimes, an entire company of soldiers was needed to complete the transportation.

"You can imagine scores of kilograms of dynamites on one's back is a real test both physically and psychologically," Fu said.

De-mining soldiers working on the front line were all technicians who had received special engineering and psychological training.

Despite the dangers, many young men were willing to join the mine-sweeping company, Sun said. "In peacetime, few military posts reflect the true value of an army except de-mining, because mine-sweeping soldiers can have the battlefield feeling."

(Xinhua News Agency December 31, 2008)