Last week South Africa, one of the last major importers of Iranian oil to seek alternative sources, tightened the knot on the noose around Tehran’s neck.South Africa’s minister of energy, Elizabeth Dipuo Peters, has announced plans to have alternative sources to Iranian crude in place by the self-imposed deadline of May. This is a significant move—and not only because South Africa gets almost 30 percent of its oil from Iran. Oil has dominated the relationship between the two countries since the 1950s, and in the decades that followed, many refineries in South Africa were designed especially to process Iranian crude. Diplomatic relations have been intermittent, but oil has been the one common interest to endure through the turbulent years of a militarized African National Congress, the Islamic Revolution of ’79, post-apartheid regime change, and the West’s most recent sanctions on foreign business in Iran.Naturally, South Africa’s dependence on Iranian oil goes a long way toward explaining its policy on Iran, and especially its support of Iran’s right to enrich uranium. But if Peters is serious about transferring oil imports to places like Venezuela and North America, its leaders may also feel freer to adopt new positions on other key policies.The sanctions are beginning to bite. The noose is tightening.