As a high-ranking officer, a lieutenant colonel should be treated with respect and dignity. When writing a letter to a lieutenant colonel, you should write the letter according to business formatting guidelines and be sure to maintain a professional and respectful tone. Be sure to include basic information such as your contact information and the date at the header of the letter and a proper salutation at the end of the letter, such as "Sincerely."
Begin the letter by addressing the lieutenant colonel as "Dear Colonel," then inserting the last name of the lieutenant colonel.
Write the body of the letter. Start with an introduction that states the reason for your contact and begin to expand from there.
Write other paragraphs of the letter as needed to communicate the message that you are trying to get across to the lieutenant colonel.
End the letter with "Sincerely," following with your signature and printed name below that.
Write on the envelope of the letter, "Lt. Colonel," then place the full name of the lieutenant colonel next to it. Write the address on the envelope as you would any other letter.