In 1795, a vast Persian army marched through Armenia and into Georgia.
Georgia was supposed to be protected by Russia, but Moscow never lived up to its commitment to defend the country.
Soon the capital city Tbilisi was sacked. For six days, the Persian army destroyed the city and murdered thousands of its citizens.
The devastation was great. It was said that the stench of rotting corpses made Tbilisi uninhabitable. As one Persian historian wrote at the time: "The brave Persian army showed the unbelieving Georgians what is in store for them at the day of judgement."
Iran is one of the established Eurasian powers and, therefore, sees itself entitled to a special status in the South Caucasus.
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During the 18th and 19th centuries, imperial Russia and the Persian Empire greatly contested the region. Often, this competition was bloody and costly for the local population, as seen in Tbilisi in 1795.
Today the situation is different. While Russia and Iran are no longer fighting each other for territorial gains in the South Caucasus, they are still competing for influence in the region.
Russia has been the winner, but this could be changing.
As a result of international sanctions, Iran has had to limit its foreign policy ambitions.
While Russia has become more assertive in the South Caucasus, even willing to use military force to advance national goals, Iran has taken a backseat in the region.
But thanks to the Vienna deal that was signed last month between the United Nations P5 1 and Iran over Iran's nuclear weapons programme, Tehran will have more resources, be more confident and less dependent on Russia on the international stage.
This will have consequences for the South Caucasus.
Iran will use its new found status and resources to get more involved in the South Caucasus - especially in Armenia and Georgia. For these two Christian countries, relations with Iran are based on the realities of geography and history.
Before the ink dried on the Vienna deal, Iran was already talking about massive investment projects in Armenia, especially in the electricity and transportation sectors. Closer Iranian relations with Armenia will make Russia suspicious.
Although Iran competes with Russia for influence in the South Caucasus, Tehran also shares the same goals as Moscow of keeping foreign influence out of the region.
During a visit by Georgian MPs to Iran, the speaker of the Iranian parliament, Ali Larijani, said that the Vienna deal is opening a "new chapter" that will expand political and economic cooperation between Iran and Georgia.
Even though Iran is able to maintain good relations with Armenia and Georgia, the situation with the other South Caucasus nation, Azerbaijan, is not as straight forward.
Although cordial on the surface, Azerbaijani-Iranian relations are fraught with tension.
Azerbaijan is one of the predominately Shia areas in the world in that Iran has not been able to place under its influence.
It has close relations with Israel, making Iran nervous. There is a large ethnic Azeri community living in Iran that has called for greater autonomy from Tehran.
Most Azerbaijanis are secular and reject Tehran's brand of extreme Islam.
Iran also disputes many of Azerbaijan's Caspian Sea claims and has even used its navy to interfere with energy exploration operations - all adding further tensions to the relationship.
However, as the United States becomes further disengaged with the South Caucasus and Moscow continues its close ties with Azerbaijan's archenemy, Armenia, it is likely that Baku and Tehran will focus on pragmatic regional cooperation.
One area that could see increased Iranian-Azerbaijani cooperation is the energy sector.
Iran has identified nearly 50 new oil and natural gas projects worth $185bn once international sanctions are lifted.
At least some of these projects will get Iranian oil and natural gas into Europe via the network of pipelines in the South Caucasus and Turkey. Azerbaijan would play a vital role in helping Iran achieve this.
Conversely, Azerbaijan wants to use Iran to get its oil to new markets.
Since the Vienna deal was signed, Tehran has revived an older oil swap agreement with Baku. Iran will import Azerbaijani oil for domestic consumption and will then export the same amount of oil from its southern fields near the Persian Gulf on behalf of Azerbaijan.
Although Iran competes with Russia for influence in the South Caucasus, Tehran also shares the same goals as Moscow of keeping foreign influence - especially the US and the European Union - out of the region.
If the US and EU are serious about closer ties with the countries in the South Caucasus, then they will need to be more engaged in the region.
Otherwise, a vacuum will be created that will be filled by unhealthy Russian and Iranian competition.
If history tells us anything, this could have deadly consequences for the region.
Luke Coffey is a research fellow specialising in transatlantic and Eurasian security at a Washington DC-based think-tank. He previously served as a special adviser to the British defence secretary and was a commissioned officer in the United States Army.
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.
Source: Al Jazeera