
From UT: The Battles of the Fords of Isen: Appendix A
In the days of Théoden there was no man apointed to the office of First Marshal. He came to the throne as a young man (at the age of thirty-two), vigorous and of martial spirit, and a great horseman. If war came, he would himself command the Muster of Edoras; but his kingdom was at peace for many years, and he rode with his knights and his Muster only on excercises and in displays; though the shadow of Mordor reawakened grew ever greater from his childhood to his old age. In this peace the Riders and other armed men of the garrison of Edoras were governed by an officer of the rank of marshal (this was Elfhelm).