U.S. Marines completed Exercise Platinum Lion 17.1, conducting multiple training operations alongside eight partner nations from the Black Sea and Caucasus regions in Novo Selo Training Area, Bulgaria, 12 Dec. to 21 Dec., 2016, to improve interoperability and tactical strength amongst NATO partners. - U.S. Marines completed Exercise Platinum Lion 17.1, conducting multiple training operations alongside eight partner nations from the Black Sea and Caucasus regions in Novo Selo Training Area, Bulgaria, 12 Dec. to 21 Dec., 2016, to improve interoperability and tactical strength amongst NATO partners.