It follows concerns over increased Russian activity in the Baltic Sea and heightened tensions in nearby Belarus.
"The focus of the high readiness action is to reinforce naval surveillance in the Baltic Sea, at sea and from the air," Jan Thornqvist, the Swedish Armed Forces' Commander of Joint Operations, said in a statement. "The military presence in Gotland is also increased."
For analysis, Radio Sweden speaks to Anna Wieslander, secretary general for the Swedish Defence Association and a director at the American think tank, Atlantic Council.
Click the play button to hear her interview.