FSB Mary Ann was initially established on 19 February 1970 by elements of the 1/46th Infantry (part of the 196th Light Infantry Brigade (196th LIB). At the time it was not intended to be a permanent base, and was closed by the same Battalion about two months after it was opened. Operational needs brought the 1/46th Infantry back to Mary Ann on 27 June, and the base was put back into operation. According to one Battalion commander it was a poor location for a firebase from a defensive standpoint. "FSB was built in a saddle with hills around it on three sides." It was also at the very edge of helicopter range from Americal headquarters at Chu Lai. Any other location in the region would have put the FSB outside the range of the Division's heavy artillery batteries and prevented artillery at Mary Ann from shelling key locations in the region. From an offensive standpoint the FSB was in a good location since it straddled the Dak Rose Trail network.