Passage: In 1962, she sailed south from Norfolk to participate in the naval blockade during the Cuban Missile Crisis. During the Vietnam War, Canberra was home ported at San Diego. She deployed to Vietnam five times from 1965 to 1969 where her 8-inch and 5-inch guns provided support for US troops. During the deployments in 1967 and 1968, Canberra operated north of the DMZ shelling bridges, transport routes and shore installations. On 2 March 1967, the cruiser was hit by two shells fired from ashore, which caused 5 injuries and minor structural damage. On 6 April 1967, a young seaman named Doug Hegdahl was accidentally blown overboard by one of the 5-inch guns; he was captured by a North Vietnamese gunboat and imprisoned in the infamous Hanoi Hilton. Hegdahl's recollections of his time there would later serve as proof of torture committed by the North Vietnamese at POW camps. At the conclusion of her second tour of duty in April 1967, the cruiser visited Melbourne, and was in Australian waters in May for commemorations of the Battle of the Coral Sea.During the 1968 Tet Offensive, Canberra went south to support the troops at Hue and fired 35,000 rounds in 31 days. On 1 May 1968, Canberra returned to her original hull number of CA-70; following the obsolescence of her missile armament, her 8-inch guns were reclassified as the cruiser's main armament, although the Terrier launchers were retained until decommissioning. Her last Vietnam deployment ended in early January 1969.

Question: What caused the armaments to become reclassified?
obsolescence of her missile armament