The Terracotta Army is traditionally believed to have been the guardians of the first emperor of a unified China, but a researcher's claim that they could have been military training models has sparked a new debate over the statues' purpose.

Sun Jiachun, a researcher with the geological bureau of northwest China's Shaanxi province, home of the Terracotta Army, said the pits where the clay figures were discovered were the ruins of a military school near the mausoleum of Qin Shihuang, the first emperor after China's unification.

Sun challenged the widely-accepted theory that the clay figures were an army corps meant to guard the emperor in his afterlife, saying they were too far away and too loosely deployed to serve as real guardians.

"The Terracotta Warriors were found at least 1.5 km from the mausoleum's outer walls," he said in an interview with Xinhua on Thursday. "They were poorly organized and were not led by a general, which contradicts ancient China's military system and traditional beliefs that a deceased emperor should be served in the same manner as when he was alive."

Sun said the huge army of Terracotta Warriors and Horses must have had a more practical function. "The first emperor and his ministers must have wanted the army to serve their kingdom -- probably by using the clay figures as a teaching aid at their military school."

Three decades into his research, Sun summed up his argument in a thesis titled "Terracotta Warriors: Ruins of an Ancient Military School," and it has been published in the latest issue of "Military History," a leading Chinese military periodical.

He elaborated on his argument in the thesis, citing the layout and structure of the pits, and prevalent military theories of the time that probably influenced the design of the pits.

The No. 1 pit, where 114 clay figures have been unearthed to date, was an underground structure, but its roof was aboveground; however, sacrificial pits around the mausoleum were all found eight to 10 meters underground, said Sun.

The inside of the No. 1 pit is 3.2 meters high and covers 14,260 square meters, with more than 20 corridors and 10 screen walls, he said. "It's open and easily accessible, like a huge hall."

The No. 1 pit is the first and largest of the three pits containing the terracotta soldiers.

Before Sun's thesis was published, renowned historian Wang Xueli also studied the clay statues from a military perspective. Wang contended that the No. 1 pit was a temporary battle grouping, the No. 2 pit was a permanent encampment, and the No. 3 pit served as barracks.

"The clay figures all faced east, as if they were on guard against enemies from that direction," said Sun, adding that the three pits containing the statues formed training and simulation grounds, and the entire site was probably a military school.

Sun said Emperor Qin Shihuang must have taken advantage of the clandestine location of his own tomb to train army officers who were expected to fight for his kingdom. "The clay figures were used to simulate battle scenes for the trainees."

His theory has sparked a new round of debate over the purpose and identity of the clay figures.

Zhang Wenli, a veteran researcher at the Xi'an-based Museum of Qin Shihuang Terracotta Warriors and Horses, insisted the figures were sacrificial guardians for the emperor.

"Sun's hypothesis of a possible military school has gone beyond archeological research. I personally believe it was an army of guardians for the deceased emperor, but in either case, we need more evidence to support our arguments," said Duan Qingbo, a professor with Northwest University.

Qin Shihuang (259-210 BC) was the founder of China's first unified feudal empire, the Qin Dynasty (221-206 BC).

His Terracotta Warriors and Horses were accidentally discovered by farmers in Xi'an's Lintong district in March 1974.

The discovery is considered one of the most spectacular findings in the annals of archaeology and is described as one of the wonders of the world.