Three sets of military exercises kicked off in Europe on Monday, involving thousands of servicemen from a variety of NATO nations and their allies, amid a wave of similar action across the area. Estonia is holding its largest-ever military drills. Named Siil-2015 (Hedgehog), the maneuvers involve about 13,000 personnel. The number includes about 7,000 reservists, along with members of the volunteer Estonian Defense League. 

Siil-2015, scheduled to last until May 15, also involves forces from the US, the UK, Germany, Latvia, Lithuania, Belgium, Poland and the Netherlands. American troops, who are staying in Estonia as part of the massive training operation Atlantic Resolve, will bring four Abrams main battle tanks to the exercise. British, Belgian and German air defense units, as well as several NATO warplanes, will also take part.The Lithuanian Army is holding its own maneuvers as part of the largest national drills called Zaibo Kirtis (Lightning Strike). The training involves over 3,000 troops. It is focused on joint action by the army and civilian authorities against so-called hybrid threats combining both military and non-military methods of fighting, according to Army Commander Major-General Jonas Vytautas Zukas. MORE