The United States, Israel, and their Western allies have, so far, failed to take military action to destroy Iran’s nuclear weapon development program, but Eli Lake explains that does not mean that covert operations intended to at least slow production have not been underway behind the scenes.

Efforts to steer defective products toward Iran have taken a number of forms. For instance, according to a former Mossad operations officer who goes by the alias Michael Ross, in 1998, the Mossad and the CIA developed a plan to sell a supposedly helpful chemical substance—which would, in fact, gum up centrifuges over time—to Iran on the black market.

Then, there was the odd case of the Tinners, a Swiss family of engineers long believed to be a cog in the network of nuclear proliferators organized by Pakistani scientist A.Q. Khan. In 2008, Urs Tinner admitted that he had been a CIA asset. And it turns out that he may have played a crucial role in an effort to sabotage Iran’s nuclear program. According to The New York Times and other sources, the Tinners sold high-quality vacuum pumps to the Iranians and Libyans. The pumps are crucial for uranium enrichment because centrifuges must operate inside a vacuum seal. David Albright—the president of the Institute for Science and International Security and the author of a new history of Iran’s illicit procurement of nuclear technology, Peddling Peril—explains that, while the pumps that ended up in Iran and Libya were produced in Germany, they were also worked on by the Oak Ridge and Los Alamos laboratories. These labs, he says, modified the pumps “to bug them or to make them break down under operational conditions. If you can break the vacuum in a centrifuge cascade, you can destroy hundreds of centrifuges or thousands if you are really lucky.” (A senior intelligence official confirmed Albright’s information to me. It should be noted that not everyone agrees that the Tinners were the ones who sold these pumps to the Iranians and Libyans; Albright, for one, isn’t sure.) …

But do sabotage efforts work? In late 2008 and early 2009, the iaea began to see a drop in the amount of low-enriched uranium (LEU) being produced at Natanz, the facility that lies at the center of Iran’s known nuclear weapons program. In the fall of 2008, its centrifuges were producing 90 kilograms a month of LEU. By the end of the year, however, the same centrifuges were producing 70 kilograms of LEU. To be sure, that number was back up to 85 kilograms per month at the close of 2009, and it has been climbing since, to around 120 kilograms a month; but those increases came after the installation of more centrifuges—all of which suggests that at least some of the machines were less efficient than they should be.

Ivan Oelrich, a nuclear scientist and the vice president of the strategic security program at the Federation of American Scientists, estimated in a study this year that the centrifuges are operating at 20 percent efficiency. “We know the average efficiency of the centrifuges is dismal. We don’t know whether it is because of the quality of the individual centrifuges or how they are linked together,” he explains. “We can’t rule out sabotage as one factor leading to these inefficiencies.” Greg Jones, a nuclear analyst at the rand Corporation, says the Iranians “are operating just under four thousand machines, but they have installed about eight thousand five hundred. Those nonoperating machines have been installed for many months. Why they are not operating is not clear.”

Among people I spoke to, there seemed to be a broad consensus that sabotage was, at the very least, slowing Iran’s quest for a nuclear weapon. A senior administration official told me that there was evidence the Iranians are experiencing delays due to “a combination of reasons—some inherent to the nature of the infeasibility of the design and the machines themselves, and some because of actions by the United States and its allies.” Explains David Kay, “History says that these things have done more to slow programs than any sanctions regime has or is likely to do.”

However, the biggest payoff from these efforts may not come from the sabotage itself, but from the psychological effect it could have on Iran’s government. At the most general level, there are probably benefits to keeping Iranian intelligence officials paranoid and off-balance, simply because it can cause them to waste valuable time and resources. This appears to be happening. In 2007, for example, Iran’s state-run news service reported that the national police had arrested a cell of spy squirrels. The next year, Iran reportedly arrested a group of spy pigeons.

But the specific benefit of sabotage is that it makes countries wary of purchasing crucial materials on the black market.