Military and policy leaders from multiple nations engage during U.S. Cyber Command's CYBER FLAG 21-1 exercise. U.S. Cyber Command’s CYBER FLAG 21-1 exercise, the largest multinational cyber exercise to date, helped more than 200 cyber operators from 23 countries bolster their defensive skills at Joint Base Suffolk, Virginia, from Nov. 15-20. Defensive cyber teams from Canada, Denmark, Estonia, France, Germany, Lithuania, Norway, the Netherlands, Poland, Sweden, the United Kingdom and others participated in CYBER FLAG 21-1.