From Joint Chiefs of Staff wiki--

Following the Goldwater–Nichols Act in 1986, the Joint Chiefs of Staff do not have operational command authority, either individually or collectively, as the chain of command goes from the president to the secretary of defense, and from the secretary to the regional combatant commanders.[7] Goldwater–Nichols also created the office of vice chairman, and the chairman is now designated as the principal military adviser to the secretary of defense, the Homeland Security Council, the National Security Council and the president.[8]