Al Qaeda has operated in Azerbai-jan since the 1990s, and terrorist plots have been foiled there before, so the announcement was not entirely surprising. What was noteworthy, however, was that some members of the al Qaeda cell had spent two months receiving “weapons and physical training in the Islamic Republic of Iran.”

Azerbaijan is on the front lines of a shadow war between Israel and Iran. At stake are Iran’s nuclear weapons program and Israel’s clandestine efforts to stop it. A recent article published by McClatchy Newspapers refers to Azerbaijan—sandwiched between Iran and Russia on the Caspian Sea—as a “den of spies.” Russia, the United States, the United Kingdom, Israel, and Iran—all of these countries and more run clandestine operations on Azerbaijani soil. “This is ground zero for intelligence work,” an Israeli intelligence official told the London Times earlier this year. “Our presence here is quiet, but substantial. We have increased our presence in the past year, and it gets us very close to Iran.”

Too close, from the Iranians’ perspective. Iranian officials routinely allege that Israel launches attacks on Iran’s nuclear scientists from Azerbaijan. Several Iranian scientists have been killed or wounded by assassins since 2010. After one scientist was killed in January, the Iranians summoned Azerbaijan’s ambassador to protest Mossad’s “activities” north of the Iranian border. “Some of the terrorists linked to the assassination of Iranian nuclear scientists have traveled to Azerbaijan,” Iran’s foreign ministry said in a statement. From there, Israel’s spies allegedly “facilitated” the assassins’ “travel to Tel Aviv.” Iran’s ambassador to Azerbaijan recently stated that his government has “documents to substantiate this claim.”

In reality, it is impossible to verify these allegations or much else about the spy vs. spy battle in Azerbaijan. The spies conducting the shadow war do not advertise the specifics of their business. The Iranians have alleged that the United States and United Kingdom have participated in the assassination campaign. But the State Department has strongly denied any involvement, and the Iranians are probably overreaching. A common motif in Iranian propaganda since 1979 has been to blame the “Great Satan” for all of Iran’s ills.

Still, it is widely assumed that Israel is behind the motorcycle-riding assassins who have targeted several Iranian nuclear scientists. Certainly, Israel has every reason to want to disrupt Iran’s nuclear efforts.

In late March, Foreign Policy magazine reported that Israel had struck a deal with Azerbaijan that would allow the Israelis to launch airstrikes against Iran’s nuclear installations from its territory. Whether or not this is true, the relationship between the Israeli and the Azerbaijani governments is close.

To counter this alliance, Iran has long sought to strike Israeli and Western targets in Azerbaijan using the mullahs’ own preferred instrument of statecraft: terrorism. In 2008, Azerbaijani authorities thwarted a plot to bomb the Israeli embassy in Baku. Several would-be terrorists were arrested, including two Lebanese citizens. The cell was reportedly operating under orders from the Iranian Revolutionary Guard Corps (IRGC) and Hezbollah, Iran’s chief terrorist proxy in Lebanon.

In January of this year, Azerbaijan’s Ministry of National Security announced that it had broken up a group of Iranian-backed terrorists who were making “preparations” to attack “foreign public figures in Baku.” Their targets included Israel’s ambassador to Azerbaijan, Michael Lotem, as well as a rabbi and teacher at a local Jewish school. The Iranians allocated $150,000 for the plot, and the terrorists’ ringleader lives in Iran, where he met “with Iranian special services.”

Then in March, the Azerbaijanis arrested 22 people accused of plotting terrorist attacks against the U.S. and Israeli embassies as well as other targets. They, too, took their orders from the IRGC. Azerbaijan’s Ministry of National Security said the men were trained in “camps around Tehran” and elsewhere in Iran. The cell’s members were native Azeris, and according to the Azerbaijani government, the Iranians worried that authorities might grow suspicious of their frequent travel to and from Iran. So the cell’s IRGC handlers met with some of them in other countries, including Syria and Russia.

It is in this context that Azerbaijan disrupted the al Qaeda-linked cell in mid-April. The Azerbaijanis did not say who had trained some members of the cell in Iran for two months, and numerous requests for further information went unanswered.

It is possible that the training was conducted by al Qaeda operatives. Al Qaeda has a substantial network inside Iran that, according to the U.S. Treasury Department, exists as part of a formerly “secret deal” between the Iranian government and al Qaeda. This network has delivered recruits to al Qaeda operatives in northern Pakistan, Iraq, Afghanistan, and elsewhere.

The al Qaeda-connected cell disbanded in April was originally assembled with help from Ibrahimkhalil “Saleh” Davudov, before he was killed by Russian security forces early this year. Azerbaijan’s Ministry of National Security describes Davudov as “linked to [the] al Qaeda global terrorist network.” Davudov had been named head of al Qaeda-affiliated terrorists in Dagestan by the notorious Chechen Doku Umarov, designated by the United Nations and the United States an al Qaeda-connected terrorist.

Umarov ordered the March 2010 suicide bombings on Moscow’s Metro, which killed 40 people, and the January 2011 Moscow airport bombing, which killed 37 people and wounded nearly 200 more. He has extensive ties to the Islamic Movement of Uzbekistan (IMU) and its offshoot, the Islamic Jihad Union (IJU), both of which are closely affiliated with al Qaeda. The IMU and IJU funnel fighters and recruits through eastern Iran into northern Pakistan and Afghanistan. According to the Azerbaijani government, some members of the al Qaeda-linked cell disbanded in April were trained in northern Pakistan by the IJU.

It is also possible that the training was conducted by the IRGC or Iran’s Ministry of Intelligence and Security. Their fingerprints were all over the earlier cells dispatched from Iran. Both have been implicated in supporting al Qaeda’s operations in Iraq and Afghanistan. One clue may be the al Qaeda cell’s ties to Syria. Prior to receiving their training in Pakistan and Iran, some members of the group spent time in madrassas in Syria, where they were indoctrinated in jihad. Interestingly, some members of the terrorist cell detained in March had also been to Syria. The Syrian government, which is fighting a substantial insurgency, has long cooperated with the Iranians in exporting terrorism.

Iran’s precise role in the al Qaeda-linked cell’s plotting against targets in Azerbaijan remains unknown. An Azerbaijani spokesman said that the cell was unrelated to the Iranian-backed operatives who were detained earlier in the year. This may simply mean that the other cells were not linked to al Qaeda. He also said the investigation is ongoing. But a clear pattern has emerged. Around the world, far beyond Azerbaijan’s borders, the Iranians are using terrorists to target the Israelis. Concurrent with the thwarted plots in Azerbaijan, similar plots and Iranian-backed attacks have been carried out in India, Georgia, and Thailand.

The shadow war over Iran’s nuclear weapons program continues. And by all appearances, al Qaeda is on Iran’s side.

Thomas Joscelyn is a senior fellow at the Foundation for Defense of Democracies.