A Portuguese Marine holds security at Pinheiro Da Cruz, Praia Da Raposa beach, Portugal, while participating in a combined amphibious assault exercise, Oct. 20, 2015, during Trident Juncture 15. Trident Juncture is a NATO-led exercise designed to certify NATO response forces and develop interoperability among participating NATO and partner nations. - A Portuguese Marine holds security at Pinheiro Da Cruz, Praia Da Raposa beach, Portugal, while participating in a combined amphibious assault exercise, Oct. 20, 2015, during Trident Juncture 15. Trident Juncture is a NATO-led exercise designed to certify NATO response forces and develop interoperability among participating NATO and partner nations.