In 1287 CE, China’s great Mongol emper…

In 1287 CE, China’s great Mongol emperor Kublai Khan received word that his navy had been crushed in Vietnam. Nearly 400 of the emperor’s prized ships, part of a massive invasion force, had become trapped in the Bach Dang River, where Vietnamese soldiers set them afire with flaming arrows and burning bamboo rafts. But how did the Vienamese leader, Tran Hung Dao, do it?

According to texts from the period, Vietnamese forces cut down hundreds of trees, sharpened their ends, and placed them in a “stakeyard” across the Bach Dang River. Then, small Vietnamese ships lured Kublai Khan’s fleet into the area just before the tides turned. As the water ebbed, long lines of stakes emerged several feet out of the water, barricading the river and preventing escape.

Today archaeologists are mapping the surviving remnants of the stakeyard.

At least some of the stakeyard lies in local rice paddies, whose mud helps preserve the wooden stakes.

They archaeologists also found that stakes weren’t the only barriers – the Vietnamese forces cleverly used existing islands and other natural obstacles in their barrier.