The track record of sanctions is decidedly mixed. Research suggests they reach their stated goals only about one-third of the time, depending on the target's vulnerability, international coordination, and the clarity of the demands.

Sanctions on South Africa helped end apartheid, and sanctions on Iran brought it to the nuclear negotiating table. But decades of sanctions on Cuba and North Korea produced suffering without regime change.

The most effective sanctions are targeted, multilateral, and tied to clear conditions for removal. When a country knows exactly what to do to get them lifted, and trusts the offer, sanctions have their best chance of changing behavior.