Since World War II, countries have pursued nuclear weapons because of their destructive power and influence as well as their deterrence value. At the same time, the great powers tried to prevent nuclear weapons proliferation. In this situation, the nuclear weapons development programs of South Africa and Israel still succeeded, but these countries did not publicize their nuclear capabilities. Why did these not disclose their nuclear weapons capabilities even if disclosure could strengthen deterrence of threats against them? This thesis examines three possible variables-security, norms, and domestic politics-to find the answer. All these factors impacted those countries' ambiguous nuclear weapons strategies, but the United States' role was most influential in how Israel and South Africa shaped those strategies. This research may contribute to better understanding possible policies of potential nuclear weapons armed states, especially in Northeast Asia.