Speculation about a possible attack on Iranian nuclear sites has reached a fever pitch over the summer. The talk is so wild that even level-headed commentators on the right like Michael Barone opine aloud that perhaps Israel won’t be the instigator; rather the Obama administration might order a U.S. strike.

This still seems beyond unlikely but there is no question that the climate has changed. True, the president’s National Security Advisor the other day reiterated the administration’s willingness for Obama to meet with his Iranian counterpart assuming certain conditions were met—conditions that no one expects will be met. But inside the White House and national security bureaucracy, opinions about Iranian behavior and intentions appear to be hardening. Robert Kagan recently recounted a briefing by the president and top officials in which they made as clear as they could that their patience with Iran has all but run out.

So what’s next? Various chess pieces have been moving but it would take a Kasparov to divine a clear strategy—on either side—from what can be observed. The United States announced a $60 billion sale of advanced weaponry—including F-15s and Apache helicopters—to Saudi Arabia, and the Israelis, uncharacteristically, have declined to voice even mild reservations. Reports of an Israeli-Saudi deal for overflight rights over the kingdom draw predictable denials but continue to surface—without causing the political uproar one would expect. An Iranian nuclear scientist who vanished last year suddenly turned up in the United States and asked to go home. Al Qaeda figures—some blood relatives of the top brass—who have been living in Iran since shortly after 9/11 have pulled up stakes. Weapons caches of Hezbollah in Southern Lebanon and (to a far lesser extent) Hamas in Gaza—both key Iranian proxies on Israel’s borders—have been growing. A fourth round of sanctions passed the UNSC with nominal Russian and Chinese support, but Moscow and Beijing undermine them any way they can. Tehran announced that a long-anticipated delivery of coveted S-300 anti-aircraft missiles had finally been made—though not from Russia, the principal seller, but from Moscow-lackey Belarus. American officials cast doubt on the “news” but nobody really knows.

Now comes word that Russia will, after a decade-and-a-half of stop-and-go work, finally fuel and start Iran’s nuclear reactor at Bushehr by August 21st. Similar word has come many times before. The Russians are, in the parlance of the region, adept at selling this particular rug over and over. Somehow the carpet never actually changes hands. Could this time be different?

Only Vladimir Putin and his immediate circle really know. It matters because, once fueled and operational, Bushehr will produce plutonium 239, which can be used to make nuclear weapons. The plant is also large, impossible to conceal or move, and relatively easy to destroy from the air. But once it has gone critical, any attempt to do so would risk the release of a radioactive plume that might kill civilians and poison surrounding areas.

This leaves any would-be attacker of Iran’s nuclear sites with a difficult choice. An attack is likely to cause collateral damage no matter how carefully it’s planned and is certain to result in a PR uproar. A radioactive release would compound both problems by several orders of magnitude. Israel in particular can expect outrage—some, but by no means all, feigned—from virtually the whole world should it move against Iranian nuclear sites. Jerusalem presumably does not wish to intensify the inevitable vitriolic reaction by causing radioactive contamination.

Which means that if the story is true, and if the Israelis judge Bushehr to be a dangerous installation, they will have to move quickly—as in, within the next week. Both are big “ifs.” Reports from inside the Israeli defense establishment suggest that they don’t fear Bushehr nearly as much as the uranium enrichment facilities at Natanz and Qom. Certainly, the latter have been operating for years and have produced thousands of pounds of highly enriched uranium, whereas Bushehr has yet to produce so much as one gram of pu239 (or one watt of electricity for that matter). Also, it’s far from clear whether Iran has the technology, much less the capability, to extract plutonium from spent reactor fuel rods.

These are fair reasons not to be worried about Bushehr right now. But they aren’t good reasons to be unconcerned forever. Pu239 is an inevitable byproduct of the operation of a nuclear reactor. Once operational, Bushehr will produce bomb fuel over time. The half-life of plutonium is 24,000 years. Having produced the stuff, Tehran’s incentive to master reprocessing will be high. And when it does, the plutonium will be ready and waiting. That incentive will only grow once/if Iran has lost or suffered a severe setback in its HEU production capability. Suddenly Bushehr would be Tehran’s only route to the bomb.

And it’s an objectively better route than HEU. Breeder reactors churn out far more plutonium, much more quickly, than centrifuge cascades can produce HEU. Plutonium also makes a better bomb: smaller, lighter, more powerful and more deliverable on a larger variety of vehicles.

The possible repercussions of an attack on Iran have been gamed out thoroughly. Opinions differ on how serious they might be. It seems reasonable to assume that adding one target to a lengthy list would not make them materially worse. Any nation prepared to incur all that risk from striking Iran’s HEU sites may as well take out Bushehr as well. If nothing else, at least the attacker could know for sure that the plant would be gone. As many opponents and skeptics of a strike have noted, no such certainty would apply to attacks on the buried and largely hidden Natanz and Qom sites. Plus, the Israelis have twice destroyed nuclear reactors in the region but never enrichment cascades. It’s hard to see what sense it would make to mount the difficult, unprecedented, uncertain operation while leaving standing the one site they know they can eliminate.

So this news—if it really is news—would appear to be one more move on the chessboard that suggests the endgame may be coming soon. A grandmaster might assume that anything he could game out, the Russians and Iranians could too. Are the Russians fueling Bushehr knowing—or even hoping—that doing so might precipitate an attack? Certainly Moscow has reasons not to welcome a nuclear armed Iran. Goading someone else into doing the dirty work has significant advantages. As does the inevitable rise in hydrocarbon prices following a Middle East conflagration.

Then again, it could be just another feint. Or the above analysis could be wrong. Or it could be right, but the Israelis decide not to act for other reasons. In chess, the players’ intentions may be unknown but at least all the moves are visible. Not so in politics.

Update (7:05 p.m.): The Wall Street Journal is reporting that the Obama administration, as part of the price for a Russian vote in favor of June’s UNSC sanctions resolution against Iran, agreed not to oppose Russian help to get Bushehr started. Their rationale is that Bushehr doesn’t pose a proliferation risk because the Russians will be reclaiming all of the plant’s spent fuel rods. This of course entails trusting three parties—the governments of Iran and Russia, plus the International Atomic Energy Agency—which have not exactly proved trustworthy on this issue in the past. It’s an odd position for an administration so committed to “nuclear zero” to take.

However, it should put to rest any speculation that the United States might be contemplating an attack of our own—at least on Bushehr. It also must complicate Israeli calculations. Israel will no doubt do what it believes it has to do. Bush administration officials reportedly communicated to Jerusalem in advance their opposition to the attack on Syria’s reactor in 2007—an attack that went forward anyway. But this time such an attack would have to take place not merely in spite of an ally’s private objections to the operation but of its public approval of the targeted project.

One of the many difficult calculations Jerusalem must make is whether a potential U.S. backlash over a strike the Obama administration doesn’t want is worse than the consequences of not striking. No Israeli government could take lightly the prospect of a serious and potentially fatal breach of relations with the United States. That’s not an existential threat. But it would be dire enough that it’s not worth risking unless the consequences of inaction truly are existential. That’s a hard and unenviable call to have to make.

Michael Anton is policy director at Keep America Safe.

Next Page