Lee fought in the Mexican–American War under General Winfield Scott as a captain. Later, Scott wrote about Lee calling him "the very best soldier I ever saw in the field." After the war, Lee helped the army build forts. In 1855, Lee became a lieutenant colonel, and joined a cavalry regiment. As a Colonel, Lee was called on to stop the "slave rebellion", otherwise known as John Brown's raid on Harpers Ferry. Brown's raid was ended in less than an hour by Lee.