Writing in policy publication World Politics Review this month, Rouzbeh Parsi, a senior lecturer at Lund University who specializes on Iran, pointed out that the forces arrayed against Rouhani have varied motivations.
"Some oppose an agreement, which by definition will require an accord with the United States, on ideological grounds," he wrote. "Others, especially parts of the IRGC (Revolutionary Guard), which have benefited financially from the skewed economic environment created by the sanctions regime, will see their profit margins threatened by an opening of the Iranian market."
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That the seizure of the vessel took place within the Strait of Hormuz indicates it was likely the Revolutionary Guard, since the group operates there with its own fleet of smaller vessels, independent of the Iranian navy, said Ilan Goldenberg, senior fellow at the Center for New American Security, a bipartisan policy think tank based in Washington.
"It probably was the Revolutionary Guard. Iran has two navies—one is the Revolutionary Guard navy, which is much less professional, much more provocative, and much more likely to cause this type of problem."
Consider: In 2007, the Revolutionary Guard seized two boats carrying 15 British sailors and marines in the waters of the Shatt al-Arab waterway, just north of the Persian Gulf. Britain said the group was on a U.N.-approved mission, while Iran accused the British of trespassing on its waters. After nearly two weeks, Iran released the hostages, with Rouhani's predecessor, President Mahmoud Ahmadinejad, calling it a "gift" to the British people.