Gustavus Adolphus of Sweden, also known as Gustav II Adolf, was a king who reigned from 1611 until his death in 1632. He is best known for his military innovations and leadership during the Thirty Years' War, a major conflict in Europe. His strategies and tactics significantly advanced the effectiveness of the Swedish army, making it one of the most formidable forces of the time. Gustavus Adolphus is often credited with establishing Sweden as a great power in Europe. His reign saw the expansion of Swedish territory and influence, particularly in Northern Europe. He also promoted religious tolerance and supported the Protestant cause, which played a crucial role in the dynamics of the Thirty Years' War.