Clashes with the Jurchen at the areas near River Yalu and River Tumen had become more frequent since King Sejong of Joseon Dynasty ascended to the throne. The Jurchen crossed the border to attack villages, and the best way to stop the attacks was to chase them to deal a blow. Knowing this, however, the Jurchen ran away before the military of Joseon arrived. Three obstacles made their chase difficult.
First, the Jurchen were waiting in ambush. If a soldier got killed in an ambush, the commander had to be punished, which prevented them from being more aggressive with the chase. Because they were slow during their cautious chase, they could not catch the enemy. Second, the military could not continue the chase in the dark, making the pursuit impossible just like the ambush. As the Jurchen, which was aware of this, used it to determine the timing of the attack, it started getting dark by the time Joseon’s military arrived. Third, Joseon soldiers had to cross the borders to attack the Jurchen. At the time, the territory of the Jurchen was part of the administrative area of the Ming Dynasty, which explains why Joseon’s military gave up on chasing the Jurchen when they reached River Yalu or River Tumen.
King Sejong thought of the ways to overcome these challenges. He first made diplomatic efforts to convince Ming of allowing them to cross the border for the pursuit. However, King Sejong was still cautious about crossing the border because only was it risky, but it would also make Ming suspicious if they crossed the border too often. The Joseon king might have been criticized for being too cautious around Ming, and the criticism would have been valid if he did not make any move afterwards.
What made King Sejong remarkable is that he always had a big picture and pushed for it even if it might have seemed that he was making sacrifices. In the end, he earned honor and trust and was able to try conquering the Jurchen twice and expand the territory.