Excerpts from Books and Wikipedia
"Gustavus Adolphus succeeded to the Swedish throne in 1611, at the age of 17. He was to lay the foundation of the modern Swedish state, and make it into a major European power. By combining technical innovations, such as the introduction of an easily maneuverable light artillery, with a fine sense of strategy, he transformed the art of early 17th century warfare. Believing attack to be the best means of defense, he recovered Kalmar from Denmark in 1613, intervened in Muscovy's 'Time of Troubles' (1605-17), and attacked Poland-Lithuania (1617-29), taking Riga in 1621. In 1630, he launched himself into the Thirty Years' War, in a bold bid to ensure the survival of German Protestantism against the onslaught of the Counter-Reformation. His death on the battlefield at Lutzen in 1632 cut short a career that was still full of promise." [DK Timelines, p. 303] "During his reign, Sweden rose from the status of a Baltic Sea basin regional power to one of the great powers of Europe and a model of early modern era government. . . . His achievement in the field of economic reform, trade, modernization, and the creation of the modern bureaucratic autocracy was as great as his exploits on the battlefields."