 From January 22 to March 18 , 1969 , 2 / 9 participated in Operation Dewey Canyon which was a sweep of the A Shau Valley and the last major offensive by the Marine Corps in Vietnam . 
 From January 22 to March 18 , 1969 , 2 / 9 participated in Operation Dewey Canyon which was a sweep of the A Shau Valley and the last major offensive by the Marine Corps in Vietnam . 
From January 22 to March 18 , 1969 , 2 / 9 participated in Operation Dewey Canyon which was a sweep of the A Shau Valley and the last major offensive by da Marine Corps in Vietnam .