How long was a newly married man free from being sent to war?

Answer: One year

A newly married man was free to stay at home for one year and bring joy to the wife he had married.

“If a man is newly married, he must not be sent to war or be pressed into any duty. For one year he is free to stay at home and bring joy to the wife he has married.”— Deuteronomy 24:5 (BSB)