Iran has announced that it is conducting large-scale military exercises near the Azerbaijani border as tensions between the two countries continue to escalate.

The exercises will involve armored units, artillery, drones, electronic warfare units and helicopters, Army Ground Forces Commander Brigadier General Kiomars Heidari announced on September 30. They were slated to begin the following day in the “northwestern regions” of Iran, Heidari said.

Iranian social media accounts, including those affiliated with the armed forces, have been releasing videos of large columns of materiel reportedly heading north.

The exercises follow shortly after another set of drills in the same region about which very few details have been released. While Iranian officials insisted that those exercises were routine, they came amid a spike in tension between the two countries and prompted sharp criticism from Baku.

In a September 27 interview with the Turkish Anadolu Agency, Aliyev said the first set of exercises were “surprising” and that they were unprecedented in the last 30 years. “Why now? Why exactly on our border? These questions are being asked by the Azerbaijani public, not me,” Aliyev said.

These new exercises appear to be sending an even more pointed message, and they have been accompanied by a flurry of jingoistic saber-rattling from Iran. One commentator affiliated with the Islamic Revolutionary Guard Corps, Hossein Dalirian, tweeted on September 30: "Just imagine that a war breaks out with Azerbaijan. The Islamic Republic can fire 1,000 ballistic missiles and hit 1,000 key points. The war will end in one day. And there will be no time to use other equipment. Do not pay attention to bragging [by Azeri officials]."

Azerbaijan had not officially reacted on September 30 to the announcement of the new exercises, but affiliated media were giving as good as they got. “Those worrying about possible Iranian attack on Azerbaijan should know that any attack on Azerbaijan has a real potential to involve regional & global superpowers,” tweeted the English-language news website Azeri Times. “Such a scenario would be a once in a lifetime opportunity for global superpowers to attack. And Iran knows this well too.”

Chest-thumping aside, that is an accurate analysis: war between Iran and Azerbaijan would undoubtedly draw in other powers, likely Israel and Turkey at least, and would be a disaster for nearly everyone – perhaps most of all Iran.

Nevertheless, the saber-rattling is real. What is not yet clear is why.

The proximate cause appears to be the detention of some Iranian truck drivers. Iranian trucks have long supplied Armenian-controlled Nagorno-Karabakh with fuel, and following last year’s war, Azerbaijan retook territory that includes small slices of the road connecting Iran to Karabakh through southern Armenia. With that restored control over the road, Azerbaijani police and border guards have been attempting to crack down on the Iranian trade.

That has been accompanied by other irritants, including a series of military exercises involving Azerbaijan, Turkey and Pakistan, and a spike in anti-Iranian rhetoric from Azerbaijani officials.

But none of that explains the seriousness of Iran’s reaction.

One notable feature of Iran’s recent rhetorical campaign against Azerbaijan is the latter’s ties with Israel. While Iran hardly needs a reason to bring up the “Zionist regime” to justify some policy or another, this talking point with respect to Azerbaijan has been activated to a conspicuous degree in recent weeks. And it only appears to be accelerating.

Iran will not tolerate its neighbors becoming “a safe haven and a base for the presence and anti-security activities of the fake Zionist regime,” Brigadier General Mohammad Pakpour, the commander of the Islamic Revolution Guards Corps Ground Force, told reporters on September 29. While Pakpour didn’t name Azerbaijan explicitly, his reference was clear. “There’s no doubt that the Zionist regime helps and supports certain regional countries with the purpose of creating disagreements and rift among Muslim nations,” he said.

“The neighboring governments are aware more than anyone else of the reasons for Iran’s war games,” Pakpour added.

But Azerbaijan’s close ties with Israel – based on gas sales in one direction and weapons sales in the other, as well as a shared mistrust of Iran – are not a new story, either. That relationship has been strong for years, although it has been newly visible since last year’s war, in which Azerbaijan used Israeli weaponry to significant effect.

Still, since the 2020 war there has been nothing new on the Israel-Azerbaijan front – at least on the surface – that would account for this heavy reaction from Iran.

Similarly, Iran has been alarmed by Turkey’s newly bolstered influence in Azerbaijan, but in that case as well there has not been any specific trigger recently.

A fuller explanation may soon emerge. For now, though, the region is going to be nervously watching northern Iran, and closely following the rhetoric coming from Baku and Tehran – not to mention Ankara, and Jerusalem, and Moscow, and…