NATO countries have begun their major military drills in southern Bulgaria. Nearly 25,000 military personnel from 22 NATO allied and partner countries are participating in The Saber Guardian 17 exercise. <br/><br/>The drills have been considered as one of the largest in the Black Sea region under the leadership of US Army. The multinational drills, which consist of air and ground-based forces, are aimed at increasing joint operational capability of the NATO allies and partner countries.