Yuwen Gui, styled Yonggui, was a man of Xiazhou during the Northern Dynasties. When his mother was pregnant with him, she dreamed of an old man holding a baby to her, saying, "I give this child to you; he will surely live long and be wealthy and noble." When he was born, he looked exactly as in his mother's dream, so his family gave him the courtesy name Yonggui.
When Yu Wengui was young, his family sent him to school for an education. As the teacher explained poetry, Yu Wengui stared out the window and sighed, "A man should wield a sword and sweat on horseback to win fame—how can he bury his head in books like a scholar?" The teacher marveled in astonishment.
During the final years of Emperor Xiaoming of the Northern Wei Dynasty, the Xiazhou governor Yuan Ziyong was besieged in his city by the rebel leader Poliuhan Baling. Yu Wengui was ordered to lead a relief force, and in over a dozen battles, he charged ahead fearlessly, earning the admiration of the entire army for his courage.
Yuwen Gui followed Yuan Ziyi on a campaign against Ge Rong, whose forces were at their peak and rampaged unchecked. Yuwen Gui lost his first battle and retreated to Ye City. As Ge Rong's massive army advanced on Ye City and besieged it, Yuwen Gui repeatedly lowered himself by rope to fight outside the walls with such ferocity that Ge Rong's troops, terrified, dared not engage him. Yet the siege dragged on, and Ye City fell into dire straits. Yuwen Gui cleverly slipped past enemy sentries, escaped the city, and brought back reinforcements, lifting the siege. This feat made his name widely known.
Ge Rong boasted he would march straight to Luoyang, his vanguard already past Ji Commandery. Yu Wengui, following Erzhu Rong with seven thousand elite cavalry, prepared to meet him at Fukou. Ge Rong, claiming a million troops, advanced arrogantly toward Fukou. Seeing Erzhu Rong's forces vastly outnumbered, Yu Wengui carefully surveyed the terrain and proposed a strategy of surprise. They split their men into small groups, hiding them in the nearby valleys, raising dust and clamor everywhere to confuse the enemy about their true numbers. As Ge Rong's army became disoriented, they circled behind and launched a sudden assault, forming a pincer attack from all sides. Ge Rong was captured in the battle, and his forces quickly collapsed. Erzhu Rong's army won a decisive victory. Yu Wengui, charging at the forefront with unmatched bravery, earned great merit and was promoted to a separate command.
Yuwen Gui galloped across the battlefield, his military exploits piling up like mountains, and thus he fulfilled the dream he had cherished since childhood.
"Wielding a sword and sweating on horseback" refers to holding a sword while riding a warhorse. Later used to describe meritorious military service.
Source: *Book of Zhou*, "Biography of Yuwen Gui"
Meaning of the Idiom: Later, the Chinese idiom "提剑汗马" came to describe how meritorious military service.