However he was already old when he obtained the gunpowder recipe from the merchant , and his later days saw the change of Dynasty from Goryeo to Joseon .
Since his inventions greatly contributed to his country , he was able to be promoted and participate in politics .
He was already old when he obtained the gunpowder recipe from the merchant , and his later days saw the change of Dynasty from Goryeo to Joseon .
Since his inventions greatly contributed to his country , he was able to be promoted and participate in politics .