1612
On October 20 1611, King Charles IX of Sweden died and was succeeded by his son, Gustavus Adolphus. On ascending the throne, Gustavus Adolphus sued for peace, but Christian IV saw an opportunity for larger victories, and strengthened his armies in southern Sweden.
In early 1612, Denmark attacked and eventually conquered two fortresses on the border between the fighting countries, Älvsborg and Gullberg, both in present-day Gothenburg. This was a major setback for Sweden, as the country now lacked access to the sea in the west. Having achieved this success, and aiming to end the war as soon as possible, the Danish command ordered an attack deep into Sweden, towards the capital of Stockholm. However, this proved to be a failure. Scorched earth methods and guerrilla warfare from the Swedish side made this a very difficult task and many of the mercenaries in the Danish army deserted since they did not receive their pay. Thus, the Danish army could never mount a serious attack on the capital itself.
Read more about this topic: Kalmar War