A small-scale tremor shook relations between NATO and its increasingly rogue member Turkey on May 3 when a Cyprus delegation was included on a ceremonial guest list. The incident provides a glimpse into the challenging future awaiting Turkey's ties with the alliance once Russia delivers its controversial S-400 missile-defense systems.

The fuss arose around a May 3 ceremony for US Air Force Gen. Tod Wolters, who was assuming his position as NATO’s new supreme allied commander for Europe. The event was held at NATO's military headquarters in Belgium.

Military personnel and civilians from across NATO’s 29 allied nations and various partners attended the ceremony with one exception: Turkey. Turkish officials refused to join the ceremony because Greek Cypriots were invited. Turkey claims the northern third of the disputed island of Cyprus.

Although NATO officials said the incident was an “error of protocol,” they didn’t retract the invitation sent to all European Union member-states along with Cyprus. Turkey’s military and diplomatic representatives, in response, didn’t join the ceremony.