Palmer was promoted to major in January 1912. He served in the First World War, being placed in command of the 9th Battalion, Royal Warwickshire Regiment in August 1914, simultaneously being appointed an acting lieutenant colonel.
In January 1912, Palmer's career advanced with his promotion to major. During World War I, he led the 9th Battalion, Royal Warwickshire Regiment in August 1914, and was also temporarily given additional responsibilities as an acting lieutenant colonel.