Rank in the United States Armed Forces is split into three distinct categories: officers, warrant officers, and enlisted personnel. Officers are the leadership of the military, holding commissions from the president of the United States and confirmed to their rank by the Senate. Warrant officers hold a warrant from the secretaries of the military departments, serving as specialist in certain military technologies and capabilities. Upon promotion to chief warrant officer 2, they gain a commission from the president of the United States. Enlisted personnel comprise the majority of the armed forces, serving as specialists and tactical-level leaders until they become senior non-commissioned officers or senior petty officers. Military ranks across the services can be compared by U.S. Uniformed Services pay grade or NATO rank code.