The countries you picked as an example is a little curious. Sanctions against Russia were really weak and limited, I don’t think anybody had any intentions for them to work at all. The sanctions of Cuba and Venezuela (or embargo in the case of Cuba) were targeted against their autonomy, i.e. countries were not OK with their economic policies so they imposed the sanctions (which were more devastating then any action by the government in Cuba). In the case of Venezuela the sanctions are targeted against a democratically elected government in favor of an opposition that was never elected. The goal here is to abolish democracy, what do you expect the Venezuelan government to do?

This leaves North Korea, which is a genuine example of sanctions not working (and in fact casing harm in them self, since the victims are often starving citizens). However threats of further sanctions have worked in the past to prevent North Korea from developing a nuclear weapons program (which they later developed anyway). So I’ll give you that one.

But now let’s turn to South Africa. The Apartheid government was supported by many rich nations throughout the late 20th century. Their crimes got worse and worse over the years. Until the international community finally came together in the last decade of the century and imposed heavy sanctions, even excluded them from participating in cultural and sporting events. The apartheid government finally collapsed and South Africa got their first democratically elected precedent that represented a majority of the nation in 1994.

But I don’t think it is fair to talk only about the failure of sanctions to actively work in this context, the alternative here (as per ancestor comment) is military intervention. I could just as easily come up with a list of countries where military intervention did not resolve anything (or left the country seriously damage):

• Cuba

• Libya

• Syria

• Afghanistan

• Yemen

• Somalia

You could make the case for Rwanda, East Timor, Cambodia, or even Nazi Germany. But those cases are more nuanced than that, and claiming that military intervention was a “response that worked” would be an inexcusable simplification of how the events unfolded.

South Africa.

Neither in Iraq. Nor in Iran.