February 28, 1969 – March 31, 1971. Operation Iron Mountain.

A security operation involving the 11th Infantry Brigade in a clear and search operation along the Song Tra Khuc River south and west to Song Re River, in Quảng Ngãi Province. US losses were 440 killed, PAVN/VC losses were 4589 killed and 137 captured. [36] [35] [69] Note: Other official reports state Iron Mountain started on March 18. Furthermore, the same report states the operation involves the Americal Division (23^rd Infantry Division). [290] *