When Saudi Arabia unexpectedly executed the prominent political dissident and Shiite cleric Sheikh Nimr al-Nimr a week ago, the Sunni Kingdom may not have known how Iran’s Shia-dominated government would respond — but it certainly knew that Iran would.

The subsequent storming of the Saudi embassy in Tehran and the Saudis’ severing of diplomatic relations with Iran may appear to have their roots in religion, but the reasons why the Saudis chose to escalate tensions via the execution in the first place actually have little to do with a Sunni/Shia divide. Instead, regional and domestic politics are the driving force behind this dangerous fight.

Riyadh sees the US nuclear deal with Iran — and more specifically, Tehran’s reintegration into global political and economic structures — as a threat to its own regional power. Iran’s economy is set to improve in a post-sanctions environment, and Tehran’s relations with Washington have gradually thawed. Saudi Arabia fears this rebalancing because it can no longer count on and benefit from American efforts to contain Iran politically, economically, and militarily. Riyadh is not being abandoned in favor of Tehran, but it will have to take a more active role in any effort to counter Iranian power.

Iran’s slow but steady regional rise is also coming at a time when Saudi power is on the decline, as evidenced by its military failures in Yemen. In November, Washington approved a $1.29 billion arms deal with Riyadh — adding to the tens of billions of dollars that Saudi Arabia has spent on American arms in recent years — and the Saudis instituted a $5.3 billion increase in military spending earmarked for its war in Yemen this past year. Nevertheless, they have been unable to defeat forces who possess much less money and far fewer weapons.

Saudi government revenue has dropped amid the plunge in oil prices, and the country’s economy is almost entirely dependent on oil revenues. This year, an approximately $100 billion budget deficit has forced Riyadh to adopt austerity measures that include price increases on gas, electricity, water, and industrial energy; the introduction of a sales tax; and delayed government payments. Over time, such changes could strain the social contract between Saudi citizens and the ruling al-Saud family.

Playing the anti-Shia and anti-Iran cards is a pretext for the Saudi government to crack down on domestic dissent, call on its regional allies to take sides against Iran, and deflect attention from its geopolitical, military, and economic failures. So far, their strategy might be working. However, trading short-term domestic stability for an indefinite period of regional instability is a roll of the dice. There is no guarantee that sectarianism can be reined in once it has been unleashed.

For its part, Iran’s response violated one of the few universally agreed-upon rules of foreign relations: Don’t storm embassies. But shortly after the embassy was ransacked, a chorus of senior Iranian political and military voices condemned the act. President Hassan Rouhani called it an attack on Iran and its reputation, and urged the judiciary to prosecute those responsible. Key Iranian officials joined Rouhani’s condemnation, including the judiciary chief and Revolutionary Guard commanders. Iran also sent a letter to United Nations Secretary General Ban Ki-moon expressing its regret, promising to arrest the perpetrators and take measures to prevent such incidents in the future. Tehran’s contrition has almost certainly been communicated directly to Riyadh.

That said, if it seems like the Iranian government’s behavior is schizophrenic, that’s because it is. A small but powerful group of hardliners is trying to derail Rouhani’s foreign policy initiatives in an effort to weaken his domestic political power. Most of Iran’s political elite believes it’s best to avoid imposing heavy costs on Saudi Arabia because the Saudis are already paying heavy costs for their foreign and domestic policy challenges. They argue that taking action against Saudi Arabia will only help bolster Riyadh’s narrative about Iranian efforts to enforce its domination over the region and occupy Arab land.

Iranian hardliners know this, which is why they stormed the embassy. They are trying to radicalize the country’s policies in an effort to eliminate their political rivals under the pretext of national security; the domestic violence undermines Rouhani’s efforts in the region at large to bring Iran out of its relative isolation. Iran is holding two important elections next month, and hardliners are trying to protect their own political power.

The degree to which Rouhani is able to follow through on his promise to hold the embassy attackers accountable will be telling. If the Iranian government is able to speak with one voice and manage the rogue actions of radicals, it will help pave the way toward de-escalating tensions with their Saudi counterparts.

The ramifications of a continuing deterioration of Iran-Saudi relations cannot be overstated. Neither one can impose their will upon the other, so they face the same dilemma: If they don’t accept each other’s power, they cannot guarantee their own security. Unless some degree of dialogue and accommodation is reached, regional insecurity will continue to be a pox on both houses. And until cooler heads prevail in Riyadh and Tehran, conflict in the broader Middle East will likely get worse before it gets better.

This piece originally appeared in Vice News.