Yan Zhan Men Du of the Jin Dynasty was a towering figure with a magnificent flowing beard. When his elder brother Yang Ai fell in the assault on Bianliang, Men Du took up arms, donned his armor, and marched into the military camp to begin his own martial career.
When Mendo served as a deputy under Ruizong, Commander-in-Chief Wanyan Gao prepared to attack Raofeng Pass and sent Mendo with sixty cavalry as an advance team to scout the terrain and enemy positions. Mendo completed the mission brilliantly, showcasing his military talent. Impressed by his quick wit, courage, and composure under danger, Wanyan Gao kept Mendo by his side.
In the early years of the Tianjuan era (1138), Li Shifu, commander of the Dingguo Army, was captured by the Jin forces along with his father. After his father was killed, Li defected to the Western Xia, biding his time to avenge his father's death. One day, Li hosted a banquet and invited the Jin general Wanyan Gao as his guest. During the feast, under the pretext of presenting armor, Li seized Gao. Seeing the dire situation, a loyal officer named Menduo risked his life to escape, rallied reinforcements, and rescued Wanyan Gao. Menduo went on to earn numerous military honors.
Mendu was a commander of steadfast loyalty and meticulous caution. In battle, he excelled at setting up camps with extraordinary precision and planning. Calm and composed even when enemies launched sudden attacks, he would remain unruffled as arrows rained down like a hailstorm, issuing orders and arranging tactics as if it were just another day. With a chivalrous heart, he treated his soldiers with great generosity and leniency, which kept their morale high and discipline firm under any circumstances. His men followed him with unwavering devotion, ready to fight to the death.
Later, the idiom "Tai Ran Zi Ruo" came to describe remaining calm and composed, without any panic, in sudden situations.
Source: *History of Jin*, "Biography of Yanzhan Mendu"
Meaning of the Idiom: Later, the Chinese idiom "泰然自若" came to describe remaining calm and composed, without any panic, in sudden situations.