Ma Yuan was a descendant of Zhao She, the famed general of the Zhao State. Zhao She was granted the title Lord of Mafu, and his descendants adopted "Ma" as their surname.
Ma Yuan had a remarkable ability to observe, analyze, and predict events with uncanny accuracy. After Wang Mang's regime collapsed, Ma Yuan fled to the Western Regions to avoid chaos, where he was highly respected by Wei Xiao, who controlled Western Sichuan. At that time, Gongsun Shu and Liu Xiu each declared themselves emperor. Wei Xiao sent Ma Yuan to visit both Gongsun Shu and Liu Xiu to assess their true strengths. After meeting them, Ma Yuan declared, "Gongsun Shu is arrogant and self-important—a frog at the bottom of a well," while he praised Liu Xiu as a true emperor. As events unfolded exactly as he had foreseen, Ma Yuan himself later took his family and defected to Luoyang.
In 32 AD, Emperor Guangwu of the Han Dynasty personally led a campaign against the warlord Wei Xiao, reaching a place called Qi in Fufeng Commandery where the terrain was treacherous. His generals urged caution, arguing that an imperial army should avoid risky paths, leaving the emperor uncertain. That night, General Ma Yuan arrived by imperial summons, and the delighted emperor immediately sought his advice. Ma Yuan calmly analyzed the situation, explaining that Wei Xiao's commanders had lost morale and were on the verge of collapse—a swift advance would crush them. To make his point crystal clear, Ma Yuan had soldiers bring rice and used the grains to build a detailed model of the Western Hills' terrain, pointing out the exact routes and positions for attack. Emperor Guangwu, visibly relieved, laughed and said, "The enemy is laid out before my eyes—I can see them as clearly as if they were right here."
The next morning at dawn, Emperor Liu Xiu ordered his troops to advance, and Wei Xiao suffered a crushing defeat.
Later, the idiom "Gathering Rice to Form a Mountain" was used to describe correctly and vividly analyzing military situations.
Source: *Book of the Later Han*, "Biography of Ma Yuan"
Meaning of the Idiom: Later, the Chinese idiom "聚米为山" came to describe correctly and vividly analyzing military situations.