The storming of Britain's embassy in Tehran, an event apparently meant to imitate the explosive events of 1979, has transformed a simmering tension between the United Kingdom and Iran into an outright diplomatic and political showdown.
Hours after the embassy was looted and partly burned by members of the Basij, a voluntary militia loyal to Supreme Leader Ayatollah Ali Khamenei, the act drew condemnations and threats of further sanctions and penalties from Canada, the United States and European capitals, and was condemned by the United Nations Security Council as the most serious attack on a foreign mission in Iran in 32 years.
British Prime Minister David Cameron described the attack as "outrageous and indefensible" and placed the blame directly on Iran's government, calling the failure to stop the attack "a disgrace."
He warned that "the Iranian government must recognize that there will be serious consequences" for the attack, and that "measures" would be considered in the coming days.
British officials said he was referring to a meeting of European foreign ministers scheduled for Thursday, where further sanctions on the Islamic regime will be imposed. French reports suggested that a complete Europewide embargo on Iranian petroleum, something that has never before been considered, will be discussed.
Canadian Foreign Minister John Baird, who has joined Britain and the United States in their intensive program to isolate Iran in response to reports of secret nuclear-research activities, echoed those remarks, describing the attack as "completely unacceptable and outrageous," and warning Canadians working in Tehran to "exercise heightened vigilance and keep a low profile."
The incident appears to show that competing branches of the Iranian government are responding to Western pressure over Iran's alleged nuclear-weapons program in different ways, and that Iranian President Mahmoud Ahmadinejad may not be fully in control of events.
Mr. Ahmadinejad was one of the youths who stormed the U.S. embassy in 1979, triggering a hostage crisis and the complete dissolution of relations with Washington. On Tuesday, he appeared eager to distance himself from the attack, issuing a statement through the Iranian Foreign Ministry expressing "regret" for "unacceptable behaviour by a small number of protesters" and adding that "the relevant authorities have been asked to take the necessary measures and look into this issue immediately."
While this suggested that the incident will not escalate into the sequence of embassy storming, hostage-taking and military showdown that dominated world politics in 1979 (the United States no longer has an embassy in Iran), it also indicated a widely reported lack of unanimity in the Tehran regime.
The protesters were members of the Basij, a body of zealots formed in November of 1979 to defend the interests of Ayatollah Khomenei, the leader of that year's revolution against the Shah. The Basij are now loyal to the Supreme Leader and often at odds with the President.
Their embassy demonstration was ostensibly to mark the anniversary of the assassination of nuclear scientist Majid Shahriyari, a key designer of Iran's ballistic missiles. Some say he was killed by Tehran authorities after attempting to defect or speak to Western authorities, but he is also the subject of popular theories involving Western, and especially British, assassination plots. (Britain is widely believed by Iranians to be the controlling hand behind international intrigues, a belief that dates back to Iran's years under British control during the Second World War.)
But the more immediate cause of the attack was Britain's imposition of tough financial sanctions on Iran, in tandem with Canada and the United States, following an International Atomic Energy Agency report that suggested Tehran may be concealing nuclear-weapons research activities. London cut off all ties between Iran's banks, including its national bank, and Britain's financial sector, probably the most severe sanctions yet imposed by any country.
In response, Iran's parliament passed a bill on Monday to withdraw its ambassador to London and to expel the British ambassador from Tehran.
It was evident from videos and films of Tuesday's event that it took place with the approval of at least some branches of Tehran's multifaceted regime. Unlike with other organized embassy protests in Tehran, there were no barricades or phalanxes of police around the embassy, and when crowds of protesters broke free and slipped under the gates, the riot-helmeted police generally stood back and watched, allowing two hours of looting and vandalism to take place before finally driving the protesters out.