HORSE MARINES is a term that refers to cavalry-men doing the work of marines or vice versa. The expression became associated with an episode in Texas in 1836, following the Battle of San Jacinto. As Maj. Isaac Burton's Texas Rangers made a reconnaissance along the coast to establish the extent and speed of the Mexican withdrawal, they sighted and captured three Mexican supply ships. Burton's detachment became known as the Horse Marines. In a broader sense the term designates, with humorous derision, almost any military or naval incongruity.
Winders, Richard Bruce. Mr. Polk's Army: The American Military Experience in the Mexican War. College Station: Texas A&M University Press, 1997.
Jim DanHill/h. r. s.