Lieutenant colonel
A Lieutenant Colonel is the second field officer grade commissioned officer rank. It will generally take an officer 16 to 22 years to rise to the rank of Lieutenant Colonel. As a result, many career officers eligible to retire after 20 years of active service retire with the rank of Lieutenant Colonel[Military-ranks].
The lieutenant colonel typically commands battalion-sized units (300 to 1,000 Soldiers) with a command sergeant major as an NCO assistant. He or she may also be selected for brigade and task force executive officer[Goarmy.com].
Usually, a battalion with 400-1200 troops is commanded by a lieutenant colonel[Britannica].
Military unit. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/topic/military-unit#ref943787
U.S. Army Officer. Goarmy.com. Retrieved from: https://www.goarmy.com/content/dam/goarmy/downloaded_assets/pdfs/advocates-army-rank.pdf
Lieutenant colonel – field officer. Military-ranks.org. Retrieved from: https://www.military-ranks.org/army/lieutenant-colonel