NATO concluded its largest-ever military drill in the Baltic Sea with the participation of member and partner countries on Sunday, amid the ongoing Russian invasion of Ukraine.

Touted as the largest-ever military drill in the Baltic Sea, NATO's Baltops 22 exercise wrapped up Sunday on the Swedish island of Gotland.

Among the nations taking part were Belgium, Bulgaria, Denmark, Estonia, Finland, France, Germany, Latvia, Lithuania, the Netherlands, Norway, Poland, Sweden, Turkey, the United Kingdom and the United States.

The participation of Sweden and Finland was notable, as both countries have applied for membership in the alliance, spurred by Russia's ongoing war on Ukraine, which started on Feb. 24.

Finland borders Russia and was invaded by the USSR early in World War II – as do the small ex-Soviet republics of Lithuania, Latvia and Estonia, which took part as NATO members.

A total of 45 ships and 7,500 personnel participated in the drill.

Swedish Defense Minister Peter Hultqvist said Russian warplanes tried to harass exercising elements near the island during the drill, calling this unacceptable.

The Baltic island of Gotland, Sweden's largest isle, is a strategically important asset that has witnessed numerous armed invasions throughout history. The island gained its current status after a brief Russian invasion in the early 1800s.