In the U.S. Marine Corps, lieutenant colonel is the second field officer grade commissioned officer rank. Lieutenant Colonels can command anywhere from 300 to 1,000 soldiers, with the assistance of a Major, several junior commissioned officers, and a Command Sergeant Major as the primary advisor. It takes an officer 16 to 22 years to reach this rank, which has the O-5 paygrade. As a result, many officers retire at this paygrade after performing 20 years of active-duty service. Lieutenant Colonel ranks above Major and below Colonel.