sentences:  Around 1700, the monarchs of Denmark–Norway, Saxony (ruled by elector August II of Poland, who was also the king of Poland-Lithuania) and Russia united in an alliance against Sweden, largely through the efforts of Johann Reinhold Patkul, a Livonian nobleman who turned traitor when the "great reduction" of Charles XI in 1680 stripped much of the nobility of lands and properties.In late 1699 Charles sent a minor detachment to reinforce his brother-in-law Duke Frederick IV of Holstein-Gottorp, who was attacked by Danish forces the following year.A Saxon army simultaneously invaded Swedish Livonia and in February 1700 surrounded Riga, the most populous city of the Swedish Empire.