Reporting from Washington—At an Iranian military base 30 miles west of Tehran, engineers were working on weapons that the armed forces chief of staff had boasted could giveIsrael a "strong punch in the mouth."
But then a huge explosion ripped through the Revolutionary Guard Corps base on Nov. 12, leveling most of the buildings. Government officials said 17 people were killed, including a founder of Iran's ballistic missile program, Gen. Hassan Tehrani Moghaddam.
Iranian officials called the blast an accident. Perhaps it was.
Decades of international sanctions have left Iran struggling to obtain technology and spare parts for military programs and commercial industries, leading in some cases to dangerous working conditions.
However, many former U.S. intelligence officials and Iran experts believe that the explosion — the most destructive of at least two dozen unexplained blasts in the last two years — was part of a covert effort by the U.S., Israel and others to disable Iran's nuclear and missile programs. The goal, the experts say, is to derail what those nations fear is Iran's quest for nuclear weapons capability and to stave off an Israeli or U.S. airstrike to eliminate or lessen the threat.
"It looks like the 21st century form of war," said Patrick Clawson, who directs the Iran Security Initiative at the Washington Institute for Near East Policy, a Washington think tank. "It does appear that there is a campaign of assassinations and cyber war, as well as the semi-acknowledged campaign of sabotage."
Or perhaps not. Any such operation would be highly classified, and those who might know aren't talking. The result is Washington's latest national security parlor game — trying to figure out who, if anyone, is responsible for the unusual incidents.
For years, the U.S. and its allies have sought to hinder Iran's weapons programs by secretly supplying faulty parts, plans or software, former intelligence officials say. No proof of sabotage has emerged, but Iran's nuclear program clearly has hit obstacles that thwarted progress in recent years.
"We definitely are doing that," said Art Keller, a former CIAcase officer who worked on Iran. "It's pretty much the stated mission of the [CIA's] counter-proliferation division to do what it takes to slow … Iran's weapons of mass destruction program."
Iran insists that its nuclear program is for civilian purposes only.
Many Western experts are convinced that American and Israeli engineers secretly fed the Stuxnetcomputer worm into Iran's nuclear program in 2010. The virus reportedly caused centrifuges used to enrich uranium to spin out of control and shatter. Neither the U.S. nor Israeli government has acknowledged any role in the apparent cyber-attack.
Nor did anyone claim responsibility after two senior nuclear physicists were killed, and a third wounded, by bombs attached to their cars or nearby motorcycles in January and November last year.
Militants waving pictures of one of the slain scientists stormed the British Embassy in Tehran last week, setting fires and causing extensive damage. Several European countries recalled their envoys from Iran after the British government closed its embassy and expelled Iranian diplomats from London.
Like the deaths, the explosions have drawn special scrutiny in the think tanks of Washington, where Iran watchers have tracked reports of unexplained blasts in Iranian gas pipelines, oil installations and military facilities.
In October, Iranian news services reported three such explosions in a 24-hour period. The blasts killed two people. Another large blast was reported last week in Esfahan, Iran's third-largest city.
Some analysts suspect that the CIA and Israel's intelligence agency, Mossad, are involved, with possible help from the MEK, a fringe Iranian group that the State Department lists as a terrorist organization, although it has many allies in Washington's foreign policy establishment. Based in Iraq, the group is believed to have links to dissident networks inside Iran.
Iran claims to have arrested dozens of CIA informants in recent months, and U.S. officials acknowledge that a handful of informants in Iran have been exposed. What they did, or where, is unknown. In October, U.S. officials announced that they had uncovered an Iranian plot to assassinate the Saudi ambassador in Washington.
Some analysts caution against assuming the CIA is orchestrating all the attacks in Iran, arguing it gives U.S. intelligence far too much credit. But that doesn't preclude U.S. support for allied spy services in Europe and the Middle East that also target Iran. Still, there is more speculation at this point than hard evidence.
A cyber expert who works closely with U.S. intelligence said he is convinced that Israel, not the U.S., launched the Stuxnet attack because U.S. government lawyers would not approve use of a computer virus that could spread far beyond the intended target, as Stuxnet apparently did. That caution, of course, presumes the lawyers knew the virus would spread, and that's not clear. The expert would not speak publicly about classified matters.
Whether the White House would authorize the targeted killing of Iranian scientists is far from certain. An executive order signed by President Reagan in 1981 prohibits direct or indirect involvement in assassinations, although the term is not defined.
President Obama has authorized the killing of Al Qaeda members and other suspected militants, including at least one U.S. citizen in Yemen.
Some analysts claim that the U.S. would not back a bombing campaign that has killed Iranian workers at oil refineries and other civilian sites. It would amount to sponsoring terrorism, a charge Washington regularly levels at Tehran.
"I do not believe that the U.S. has participated in either attacking scientists or physical attacks against Iranian nuclear facilities," said Greg Thielmann, a former State Department intelligence official who helped expose the faulty intelligence cited by the George W. Bush administration before the 2003 invasion of Iraq. "Selling them bad parts, introducing malware — that does seem to me within the realm of what one might expect from U.S. intelligence activities."
Reuel Marc Gerecht, a former CIA operative who specialized on Iran, said he doesn't believe that the CIA could mount a sophisticated covert campaign of sabotage inside Iran, where the U.S. has not had an embassy since 1979. Gerecht long has urged the CIA to mount more aggressive operations against Iran.
"I just think trying to maintain and run a paramilitary covert action group inside Iran is beyond America's covert capacity," he said.
Whatever the cause, headlines about unsolved killings, unexplained explosions and sinister computer viruses have rattled Iranians, especially those who work in the nuclear program, analysts said.
Perhaps that's the point.
"All these things have a profound effect," Clawson said. "You have to watch your back when you go to work. You're not certain what's going to happen when you turn on your computer. You're not certain whether you can talk to your colleagues."