During the Eastern Han Dynasty, Geng Yan of Maoling, Fufeng Commandery (present-day northeast of Xingping County, Shaanxi Province) was inspired by military drills as a child and resolved to study warfare, later joining Liu Xiu's army where he earned repeated merits, was appointed a general, and became a key figure in Emperor Guangwu's rise and consolidation of power.
During the Eastern Han Dynasty, Emperor Liu Xiu sent General Geng Yan to attack the powerful warlord Zhang Bu, who controlled twelve commanderies in Qingzhou. Zhang Bu's army was strong, making him a formidable opponent. Learning of Geng Yan's advance, Zhang Bu ordered his general Fei Yi to defend the key cities of Lixia, Zhu'a, and Linzi. Geng Yan first captured Zhu'a, then used strategy to take Lixia and Linzi. Panicking, Zhang Bu personally led a counterattack on Linzi, sparking a bloody battle outside the city walls. In the fight, an arrow struck Geng Yan's thigh, but he bravely cut off the shaft with his sword and continued fighting despite the wound. When Liu Xiu heard the news, he set out with reinforcements. Before they arrived, Geng Yan's officer Chen Jun suggested a temporary retreat, citing Zhang Bu's superior numbers. But Geng Yan refused, saying, "We cannot leave our difficulties for others to solve." After a fierce struggle, he decisively defeated Zhang Bu. Days later, Liu Xiu arrived in Linzi to reward the troops. Before his generals, he praised Geng Yan: "You are like the legendary charioteer Zaofu, covering a thousand li in a day—your speed and courage are unmatched!" This story gave rise to the idiom "A Thousand Li a Day," used to describe extraordinary progress or talent. Source: *Book of the Later Han*, "Biography of Geng Yan".
"Back then, Han Xin broke through Lixia to establish his foundation; now you have conquered Zhu'a and achieved successive victories—the two feats are comparable. Earlier, in Nanyang, you proposed pacifying Zhang Bu, and I thought your ambition was too great and success unlikely. Now I realize: where there's a will, there's a way!"
Later, the idiom "Where there's a will, there's a way" came to describe that with firm determination and resolve, one can ultimately achieve success.
Source: *Book of the Later Han*, "Biography of Geng Yan"
Meaning of the Idiom: Later, the Chinese idiom "有志竟成" came to describe with firm determination and resolve, one can ultimately achieve success.