Spanish warship to lead NATO 'Formidable Shield' exercises By The frigate ESPS Cristobal Colon of the Spanish Navy will be the flagship of NATO's Formidable Shield 2021 exercise, beginning on May 15. Photo courtesy of Spain Ministry of Defense May 3 (UPI) -- The Spanish Navy's frigate ESPS Cristobal Colon will lead a multination interoperability exercise off the Portuguese coast, the U.S. Navy announced on Monday. The two-week exercise, known as Exercise At-Sea Demo/Formidable Shield 2021, will begin May 15 under the direction of the U.S. Sixth Fleet, and be conducted by NATO's Naval Striking and Support Services. Advertisement Fifteen ships, at least 10 aircraft and about 3,000 military personnel representing Belgium, Denmark, France, Germany, Italy, the Netherlands, Norway, Spain, Britain