Sweden wins a major victory at the <a href="https://en.wikipedia.org/wiki/Battle_of_Breitenfeld_(1631)" id="mwQw" rel="mw:WikiLink" title="Battle of Breitenfeld (1631)">Battle of Breitenfeld</a> against the Holy Roman Empire during the <a href="https://en.wikipedia.org/wiki/Thirty_Years'_War" id="mwRA" rel="mw:WikiLink" title="Thirty Years' War">Thirty Years' War</a>.