This Friday marked the beginning of the Hajj. Every Muslim must live in accordance with five essential pillars, and The Hajj–one of these pillars–stipulates that every Muslim must make a pilgrimage to Mecca, Saudi Arabia at least once in their life as long as they are able to do so. Thus millions of Muslims from dozens of sects and countries converge on Mecca each year to fulfill the Hajj. This year, however, there will be a significant absence. There will not be any Iranians in Mecca.

If we look into the past to find why exactly Iran is boycotting the Hajj this year, there a few different dates that could be pointed out. Many would agree that the conflict began on January 2, 2016. Others would point to September 24, 2015. Others would go further back and single out February 11, 1979. Still more would go even further to June 8, 632. Most would agree, however, that his year’s Hajj has become the latest flashpoint in the increasingly tense cold war between Iran and Saudi Arabia.

On September 24, 2015, a catastrophe rocked Mecca. Around 2,400 pilgrims were crushed to death in a stampede during The Hajj. Over 400 of those were from Iran. As a result, the Iranian government has been harshly critical of Saudi authorities. It has accused them of being unable to successfully administer The Hajj and protect foreign citizens. For this reason, it has barred its citizens from participating this year. Iranians were not the only foreign citizens who perished, however. Why, then, has Iran been more critical of Saudi authorities than other countries? Well, there some political reasons. Or religious ones, depending on who you ask.

On January 2, 2016, the Saudi government executed a Shia cleric by the name of Sheikh Nimr al-Nimr. He was accused of inciting violence by the Sunni Saudi government, although most foreign observers believe his execution was merely a means to silence criticism. After al-Nimr, who was very popular in Shia Iran, was executed, Iranian protesters broke into the Saudi embassy in Tehran. As a result, Saudi Arabia severed diplomatic ties with Iran. Thus it was in this state of heightened political tensions following the execution of al-Nimr that Iran has decided to bar its citizens from attending The Hajj.

Like Saudi Arabia, the United States also broke ties with Iran following an incident at their Tehran embassy. While the similarities shared by these two events may seem coincidental, they are, in fact, related. This is because the root of the political tensions that were inflamed by the execution of al-Nimr can actually be found even further back in history on February 11, 1979. It was on this day that Iran overthrew its monarchy and established an Islamic republic. Before 1979, Iran was like Saudi Arabia and the gulf states in that it was controlled by a pro-western monarchy. Revolutionaries derided this status quo, claiming the the Shah–the king of Iran–was a puppet of the west who was allowing the country to be contaminated by western culture. It is natural, then, that Saudi Arabia’s western-backed monarchy would feel threatened by this anti-monarchial and anti-western way of thinking. When this way of thinking came to power in Iran through the revolution, it legitimized an alternative to the Saudi model of government. As a result, a political rivalry was born.

Some, however, would argue that the roots of the Iran-Saudi Arabia go back even further. Back to June 8, 632. It was on this day that the prophet Muhammad–the founder if Islam–passed away. His death raised the question of who would succeed him as the religious and political leader of the Islamic world. Some supported Abu Bakr, who was one of Muhammad’s closest friends and confidants. Others believe that Ali, Muhammad’s cousin, was chosen by Muhammad as his rightful successor. This disagreement resulted in the first split of the Islamic world into its two major sects. Supporters of Abu Bakr eventually came to be known as Sunnis, and the supporters of Ali came to know be known as Shias. Iran is the most powerful Shia country while Saudi Arabia is the most powerful Sunni one. Because of this, many view the rivalry between the two countries as a continuation of the religious differences that have divided them for centuries.

Do we have our answer, then? Is Iran boycotting The Hajj this year because Muhammad’s death resulted in a succession crisis in 632? Well, it isn’t that simple. Whenever a conflict arises in the Middle East, the split between the Sunnis and Shias is often cited as its root cause. Despite its convenience, however, we should be wary of using this centuries-old religious conflict as a scapegoat. In reality, it is the power dynamic between the two countries that has resulted in Iran’s decision to boycott The Hajj.

Like the United States and the Soviet Union, Iran and Saudi Arabia are engaged in a cold war. Just as those two countries emerged as the two global superpowers following the Second Word War, Iran and Saudi Arabia have emerged as the two most powerful countries in the Middle East, and each threatens the other. The Kings of Saudi Arabia fear a revolution like that which toppled the monarchy in Iran, and the mullahs of Iran fear a popular rejection of their anti-western ideology in the face of Saudi Arabia’s vast wealth and prosperity. By bolstering their own power and attacking the power of the other, the two countries are attempting to prove the legitimacy of their own model of government so that it will not be replaced by the other’s. The boycott of the Hajj is merely an attempt by Iran to delegitimize the Saudi government, and the prescence of religious conflict merely offers a way for each government to justify their conflict.

While the United States and Soviet Union may have justified their conflict with airy proclamations of protecting “freedom” from “tyranny” and protecting “the proletariat” from “the bourgeoisie,” what the leaders of both countries really wanted, whether consciously or subconsciously, was to guarantee prosperity for themselves. It is for this reason that they worked perfectly well together when united against the common threat of nazism and only turned against each other once both had developed a nuclear weapon.

In the same way, the leaders of Iran and Saudi Arabia are using religious conflict to justify their political rivalry. The esoteric religious divisions between the Sunnis and Shias are not enough, in and of themselves, to cause conflict. It is the instinct of self-preservation among the leaders of the two countries that will keep the Shia-Sunni conflict alive, it is this instinct of self-preservation that will keep Iran and Saudi Arabia from working together until the interests of their leaders align, and it is the very same instinct of self-preservation that will keep Iranians out of Mecca this year.