KEY POINTS
  • The reasons behind Turkey's opposition to Sweden and Finland joining NATO are complicated, emotional and steeped in decades of often violent history.
  • Turkey says Sweden has supported members of the Kurdish Workers' Party, or the PKK. Sweden denies this.
  • Since 1984, between 30,000 and 40,000 people are estimated to have died in fighting between the PKK and Turkish government, according to Crisis Group.

When Finland and Sweden announced their interest in joining NATO, the two Nordic states were expected to be swiftly accepted as members of the defense alliance. But joining NATO requires consensus approval from all existing members, and Turkey – one of the group's most strategically important and militarily powerful members – is not happy. 

The reasons why are complicated, emotional and steeped in decades of often violent history.