It is also stated that Gustavus knew Greek, and read Xenophon in that tongue, of whom he said “that he knew of no writer better than he for a true military historian.”
For some years after Gustavus ascended the throne, he is said to have devoted an hour each day to reading, preferring to all others the works of Grotius, especially his treatise on “War and Peace.”
Young Gustavus possessed great courage, to which was joined striking benignity of character which he did not inherit from his parents. King Charles was stern and somewhat heartless, and he was persuaded by his wife, the mother of Adolphus, to great acts of cruelty towards the victims of his civil wars, which obscured his nobler qualities. The mother of Gustavus, though possessed of a strong and positive character, was too tyrannical to be attractive, and too unrelenting to exert a loving influence in her household, and the severity of both husband and wife came often in collision. Adolphus was the only member of the royal family who dared attempt to pacify his father when he was angry. Though Gustavus inherited the strong characteristics of his parents, and possessed his father’s failing of a quick temper, his nature was so sympathetic and unselfish that his winning manners attracted the hearts of all as much as the unrelenting sternness of his parents repelled. Their sternness became in the household only exacting selfishness; whereas all the severity of his character manifested itself only in unflinching allegiance to the right and true, and the steadfast upholding of high and noble principles of state or religion. Gustavus was scarcely fifteen years of age when he requested to be placed in command of troops in the war against Russia. But his father, deeming him too young, refused. When he was seventeen years of age, war having been declared with Denmark, young Gustavus was pronounced in the Diet—as the assembly of the Swedish nobles was called—fit to bear the sword, and he was, according to ancient custom, invested with this dignity with most splendid ceremony.
In this expedition young Gustavus endured his first trial of warfare, being present at all the remarkable encounters, holding chief command in most of them. For during this war King Charles died, and the command was left to Gustavus, then seventeen years of age. In the first month of his eighteenth year, he received the crown in the presence of all the representatives of the estates of Sweden, at the Diet of Nyköping. He took the title of his father,—king-elect and hereditary prince of Sweden, of the Goths, and of the Wends. Since the death of Gustavus Vasa, his grandfather, a period of more than fifty years, Sweden had not enjoyed a single year of peace.