13. Delta Force – United States
AKA 1st Special Forces Operational Detachment-Delta (1st SFOD-D), Delta is specialized in counter-terrorism within and other unconventional warfare operations. Unlike the Navy SEALs, much of their whereabouts is unknown and even the operators are not allowed to publicly disclose their occupation to the public. All we know is that they are a branch of the U.S Army special forces and requirement to be selected requires at least 2 years serving in the army.