Few references are found in Chinese writings to the use of the hot-air balloon principle. Perhaps it was for a long time not thought worthy of much attention, but by medieval times the military possibilities were being exploited. There are several references in European chronicles to the use of hot-air balloons, shaped like dragons, either for signaling or as standards by the Mongol Army at the Battle of Liegnitz in 1241. The principle was in all probability obtained from the Chinese; the Mongol Dynasty finally established full sway over all of China only nineteen years after this.
Needham has pointed out that paper was available in China so many centuries before anywhere else (from the second century BC) that "the development of the classical globular lanterns would have encouraged experimentation. -When their upper openings were too small and the source of light and heat unusually strong, they must sometimes have shown a tendency to rise and float free of support."
A vivid eyewitness description of the use of hot-air balloons in the form of paper lanterns is provided by Peter Goullart, who lived between 1939 and 1949 in the Lichiang region of Yunnan Province in the south of China:
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