What change occurred for the Navajo Code Talkers in 1969?

The correct answer highlights the significant change that occurred in 1969 when the Navajo Code Talkers were granted permission to speak about their service during World War II. For many years, the use of Navajo as a code language was a closely guarded secret due to its military importance. Following the war, the contributions of the Code Talkers were not widely recognized or celebrated, and many were prohibited from discussing their experiences, leading to a lack of public acknowledgment of their crucial role in wartime communications.

In 1969, this policy changed, allowing the Navajo Code Talkers to share their stories publicly, which marked a pivotal moment in recognizing their contributions and valor. It opened the door for greater acknowledgment of their service not only within the Navajo Nation but also in the broader national context. This change was foundational in celebrating their legacy and contributions to military history. The other choices, while they may sound significant, do not specifically refer to the notable shift in policy regarding their ability to speak about their experiences, which is why this answer captures the essence of the change that occurred at that time.