The enlistments of Johnston's volunteers ran out just before the Battle of Monterrey. Johnston convinced a few volunteers to stay and fight as he served as the inspector general of volunteers and fought at the battles of Monterrey and Buena Vista. Future Union general, Joseph Hooker, was with Johnston at Monterrey. Hooker wrote: "It was through [Johnston's] agency, mainly, that our division was saved from a cruel slaughter... The coolness and magnificent presence [that he] displayed on this field... left an impression on my mind that I have never forgotten."