Answer
At the time of his death, Dmitry Donskoy, the Grand Prince of Moscow, was 39 years old. He ascended to the throne at the tender age of nine, following the unfortunate demise of his father, Ivan II the Fair. Throughout his reign, Dmitry demonstrated exceptional leadership and military prowess, notably in the Battle of Kulikovo in 1380, where he valiantly led his forces to victory against the formidable Golden Horde.