The Rwandan genocide occurred for a variety of reasons, but the trigger was the death of President Habyarimana on his plane ride back from peace talks with Tutsi Rebels in Tanzania in April of 1994. Essentially Rwanda has three ethnic groups: Tutsi, Hutu and Twa (who are an extreme minority). Germans gave the area to the Belgians who allowed the Tutsi (15%) to rule the Hutu majority (85%). Some people say that the Hutus and Tutsi were "created" by the colonizers, but this seems to be a national myth to bring the country together (there are no more official tribal designations after the genocide) . The problem came after WWII when the Belgian colonists tried to create an independent state with Hutu leadership. Tutsis fought in a new power struggle which got worse after 1957 when chief Matara III died without an heir. Without going into too much depth, the fighting and fragmentation got worse as French Catholics supported a new Hutu leadership and Tutsis tried to overthrow the government in the 60's and 70's. In the summer of 1994 more than 1 million people were killed by Hutus around the country. Tutsi rebels who had gone into exile in Uganda, Congo, Brundi and Tanzania returned and ousted the Hutu government. Paul Kagame was the general who reinvaded and stopped the killings and is the current president. France and the USA are accused by many Africans of holding back the UN and thus allowing the killings to continue. French favored the Hutus as they were Catholic and wanted to continue using the French language while the Tutsi favored changing to English, and trained the Hutu army. The US is accused of not using its power to step in and stop the killings with UN forces and refusing to acknowledge a "genocide" was taking place.

Source- History of Africa Vol II by Assa Okoth

edit: took out the part where I mention Kagame as being seen as a benevolent dictator to comply with subreddit rules

While there's a lot of answers dealing with the 20th century Rwandan issues. I think to truly understand this issue (and in regards to the question) the details of European colonialism must be dealt with. The Hutu-Tutsi conflict was one that was in many ways fabricated by Europeans during their colonial rule. In modern day African scholarship it is generally agreed upon that "Tribalism" or tribes in many parts of sub-Saharan Africa were fabrications by the Europeans who were colonizing to justify colonial practices. In Rwanda specifically I would recommend Mahmood Mamdani's book When Victims Become Killers which explains much more fully than I can here the Rwandan genocide in general.

Pre colonial Rwandan Society

So directly prior to colonialism the Rwandan state was a somewhat centralized polity that Incorporated a number of peoples under the rule of the King or Mwami. The labels Hutu and Tutsi certainly existed and were used to describe certain peoples in the state. Historians today agree that they were not racial. The idea of race as we know is a fabrication and it probably didn't exist for pre-colonial Rwandans. These labels were generally used for denoting what proffession a person was involved in and as a result what socio-economic group they belonged to. The label Hutu was generally given to agricultural workers, these were generally the poorer members of Rwandan society. The label Tutsi was given to pastoral cattle keeping members of Rwandan society that were considered to be richer or more well off. Prior to colonialism possession of cattle was the best signifier of wealth. A Hutu who gained cattle might become a Tutsi, just as a Tutsi who's cattle died or lost his cattle might become a Hutu. The Hutu and the Tutsi generally speaking lived in close proximity and both members of society were needed for a functioning state.

There are several oral traditions that are used to create the depiction of Rwandan society and most generally state a god created the everything including the Mwami (to rule) the Tutsi (as a kind of taskmaster) and the Hutu (as laborers). The traditions all say however that the rulers had a divine origin but never a foreign origin (this will be important later). All of the socio-economic Rwandan Groups were native to Rwanda and were believed to have lineages dating back to their mythical creation.

Colonialism

Rwanda was actually colonized by two different European powers. Firstly Rwanda was colonized by the Germans, post World War One the territory was given to the Belgians. The Germans naturally had some effect on the Rwandan population with the annexation of the state and introduction of colonial policies, but it was the Belgian colonizers that had the most significant impact.

When the Europeans arrived at Rwanda what they actually saw was a very complicated state that was not the primitive "tribalism" that they were expecting throughout Sub-Saharan Africa. Essentially the colonizers needed a justification for the annexation of the state and the exploitation of the area for the European use. Colonizers entered the continent with the justification that they were civilizing it, not exploiting it. As such the Catholic Church offered the Hamitic Hypothesis. The Hamitic Hypothesis (which is now considered completely wrong) posited that a group of Mediterranean people who followed Ham (one of Noah's sons) were punished and blackened by god with the mark of Ham. These people in Europeans eyes were to be distinguished from the supposedly primitive Negroids who were the Africans that needed to be civilized and were enslaved centuries prior. The actual Hypothesis changed several times over colonial rule, but that's the gist of it.

So the Hamitic Hypothesis was applied to Rwandan society. The Rwandan King and the Tutsi's were deemed to be Hamitic peoples who had migrated south from the Mediterranean. These people were higher up on the colonial racial hierarchy and given special privileges as a result. In order to justify this the creation of a new origin myth, that of an invader from the north was created by the Europeans. The Hutu on the other hand who were at the time lower on the socio-economic scale were deemed to be Negroid and thus the lowest on the racial hierarchy. As such the racial groups of Rwanda were created.

Post Colonialism

After Rwanda becomes independent in 1961 the people of Rwanda generally created the narrative that the colonial invaders had been overthrown. However, in the eyes of the Hutu majority another invader still existed. As a result of the colonial racial theory the Tutsi were not neighbors but invaders who had been exploiting the Hutu for centuries before colonialism. The Hutu and Tutsi identities were not fluid socio-economic labels but now hard racial boundaries that defined who one was in Rwandan society.

I will skip the narrative of the lead up to genocide and the death of Juvénal Habyarimana because it has already been covered in other top level comments. However, the racial boundaries that placed one group as an invader is what fueled the genocide ideologically. In direct answer to your question, the genocide had a great deal to do with Europeans/colonialism. It was the Europeans colonial societies that created the conditions for the genocide to happen. We can only speculate what would have happened without colonization, but we do know that a state existed without large scale Hutu-Tutsi conflict prior to colonization.

In terms of practical "boots on the ground" work, the UN mission there saw it coming, asked for more help and were ignored and rejected by the UN particularly thanks to the US and France. In addition, the troops there were not those of experienced peacekeeping nations (iirc, it was Bangladeshi and Nepali troops). The memoir of the UN commander on the ground, Romeo Dallaire, is a must read as he does point out that with only about a thousand more troops, he could have stopped it from happening.

Source: Shake Hands with the Devil, Gen Romeo Dallaire

Politics graduate here; studied Ethnic Conflict and Rwanda's genocide in particular.

As a brief overview: The colonial legacy was crucial in the lead up to the Rwandan genocide, but there were also several contemporary issues (particularly involving the behaviour of Rwanda's political Hutu elite) that ignited the violence.

The colonialism impact, in short:

• The creation of separate identities by the Belgian colonialists. Hutu and Tutsi identities were designated to the population based on physical differences such as lighter skin and thinner noses in the 'Tutsi' population.

• Economic differences played a part in the Belgian's identification (which becomes crucial later on), and poor Tutsis could become Hutu, while wealthy Hutu could become Tutsi. These changes were, however, rare, given the differences in opportunities for members of each group.

• Tutsis were designated to be more suitable for ruling, helping to create the inequalities and tensions between the 'ethnicities'

• When the Europeans left, the ethnic identities were largely fixed and the Hutu people resented the Tutsi's superior wealth and power. They regarded them as puppets of colonialism or even as invaders from the North (historical myth played on by the Hutu elites).

Colonialism, therefore, played a huge part in creating the differences among the Rwandan population. These differences were then exacerbated and used by the political elites in a quest for more power. The use of free radio propaganda was particularly effective in building up tension and eventually inciting genocide.

Sources include: Melvern 'A People Betrayed: The Role of the West in Rwanda's Genocide' Mullen - 'Ethnic Hatred: Genocide in Rwanda'

So I tried initially to answer this last night, but I was a tad too...incapacitated. Now I will answer, because I feel like I know plenty about this (and it'll help me remember what I learned as I consult the texts again).

Before Rwanda achieved independence from Belgium in 1962, the Tutsis (they made up 15% of the population) were historically given greater privileges in Rwanda. They were a more privileged class, and cooperated far more with the Belgians. However, upon independence, Hutu majorities (the other 85% of the population, pretty much) took over governance for three decades. During those three decades, there were systematic moments of discrimination against Tutsis, and even mass killings and violence sanctioned by the government.

In 1990, a group of armed exiles (Tutsis) clustered on the border of Uganda, and invaded Rwanda. These rebels, known as the Rwandan Patriotic Front, did gain significant advantage over government forces until a 1993 Tanzania-brokered peace talk agreement (called the Arusha Accords) was made. Here is how this was described by Samantha Powers (currently the US ambassador to the UN) based on interviews she conducted and information she gathered (as a journalist at the time):

Under [the Arusha Accord's] terms the Rwandan government agreed to share power with Hutu opposition parties and the Tutsi minority. UN peacekeepers would be deployed to patrol a cease-fire and assist in demilitarization and demobilization as well as to help provide a secure environment, so that exiled Tutsi could return. The hope among moderate Rwandans and Western observers was that Hutu and Tutsi would at last be able to coexist in harmony.

This, obviously, was not to be. Romeo Dallaire, then a major general in the Canadian army who at the time of the genocide was the commander of the UN Assistance Mission in Rwanda, and he was flown in very unprepared for what he would later confront. Again, citing Powers:

The sum total of Dallaire's intelligence data before that first [preliminary reconnaissance] trip to Rwanda consisted of one encyclopedia's summary of Rwandan history, which Major Brent Beardsley, Dallaire's executive assistant, had snatched at the last minute from his local public library. Beardsley says, "We flew to Rwanda with a Michelin road map, a copy of the Arusha agreement, and that was it. We were under the impression that the situation was quite straightforward: there was one cohesive government side and one cohesive rebel side, and they had come together to sign the peace agreement and had then requested that we come in to help them implement it."

Essentially, the UN's choice for running the Rwanda mission (through less fault of his own, more of the international community) was woefully unprepared and unaware that extremists were unhappy with the Arusha Accords. Still, he felt he would need at least 5,000 troops to help keep the agreement. Here was what happened next:

Dallaire reluctantly trimmed his written request to 2,500. He remembers, "I was told, 'Don't ask for a brigade, because it ain't there.'"

The Rwanda mission received very low acknowledgment and attention from the UN. There were over 70,000 peacekeepers around the world at the time, on 17 missions. There really weren't many people devoting that much attention to Rwanda, at least in the UN. This wasn't made any easier, thanks to the United States Congress owing half a billion in peacekeeping costs and UN dues. UNAMIR, the United Nations Assistance Mission in Rwanda had a dearth of good equipment as well. They had hand-me-down vehicles from the Cambodia mission, and only 80 of the 300 that were sent to Rwanda were usable. Medical supplies ran out in March of 1994, and there was "no money for more". Rwanda was one of Africa's poorest nations, so local resupply was pretty much a no-go. Even ammunition was in short supply.

Powers describes some of what Dallaire also revealed about the mission at the start, regarding the troops from 26 nationalities he commanded:

Whereas Belgian troops turned up well armed and ready to perform the tasks assigned to them, the poorer contingents showed up "bare-assed," in Dallaire's words, and demanded that the United Nations suit them up. "Since nobody else was offering to send troops, we had to take what we could get," he says. When Dallaire expressed concern, he was instructed by a senior UN official to lower his expectations. He recalls, "I was told, 'Listen, General, you are NATO-trained. This is not NATO.'" Although some 2,500 UNAMIR personnel had arrived by early April of 1994, few of the soldiers had the kit they needed to perform even basic tasks.

Already, you can tell this is going to be a recipe for disaster. Extremists were gathering, especially among the Hutu majority, and the UN was ill-equipped to handle or address anything going on. However, the UN mission still noticed the insane amount of militarization going on. How could they not? There were machetes being flown in, in far greater numbers than anyone could need, just as one example. In January of 1994, a Hutu informant said to be high up in the government told Dallaire that in Kigali, Hutu extremists had been ordered to register all the Tutsi. This is reminiscent of Nazi policies, if memory serves. The informant said "in 20 minutes my personnel could kill 1,000 Tutsis". He also said that the plan was to provoke and kill Belgian peacekeepers, to get Belgium to back out (taking the best-armed troops out of Rwanda). UNAMIR prepared, in response, to raid Hutu arms caches. Dallaire was called off by Kofi Annan's deputy (he was UN Secretary-General at the time). The US, and the Belgians, refused to reinforce the mission, and Annan knew that the US had already expressed opposition to "aggressive peacekeeping".

All it took now was a match. A tiny spark would ignite a volcano of violence, genocide, and death, and the UN mission would effectively be a man with his hands tied behind his back trying to build a wall to stop the flow of lava. In short: it was going to go badly.

On the evening of April 6th, 1994, Rwandan President Habyarimana's Mystère Falcon jet, a gift from French President François Mitterrand, was shot down, with Habyarimana and Burundian President Cyprien Ntaryamira aboard. Suddenly, Rwanda's president and Burundi's president were dead. Rwanda's president, keep in mind, was a Hutu. This is important.

Government soldiers and Hutu militias declared a curfew immediately, and put up roadblocks around the capital. In the weeks that followed, the US would ignore expert opinion in favor of discussing the logistical impossibilities of intervention, and the UN mission would essentially fall apart. Why? Well, it began with the Hutu moving on the house of Prime Minister Agathe Uwilingiyimana. Hutu extremists, upon the death of the president, immediately moved to take control of the streets of Kigali (where people had been forced to register if they were Tutsis, remember), and Dallaire felt that the Prime Minister would be targeted (as he was considered a reformer, and in favor of the Arusha Accords). Dallaire sent five Ghanian and ten Belgian peacekeepers (pretty much the best trained/outfitted troops he had) to protect the Prime Minister, and deliver her to Radio Rwanda, where she could make a plea for calm.

Joyce Leader, the second-in-command in the US's embassy in Rwanda, lived next door to the Prime Minister, and was hiding behind her steel-barred gates in her embassy-owned house. She got a call from the Prime Minister, begging her to let her hide there.

A peacekeeper tried to get the Prime Minister over the wall, but the extremists saw it in progress and gunshots were heard. The Prime Minister abandoned the effort, and tried to get into another compound, where the extremists hunted her, her husband, and her children down. They were then killed after surrendering to the extremists. Cheers could be heard from the militiamen after this happened. The moderate leadership of Rwanda was hunted down in similar fashion during this time.

This wasn't all of what happened. The extremists rounded up the Prime Minister's Belgian guards, separating them from the Ghanian ones, and took them to a military camp (leaving the Ghanians to get to safety). They then killed and savagely mutilated the Belgian troops. Suddenly, Belgium was hearing huge calls for either expanding UNAMIR's mandate or removing the troops was heard. As you can imagine, the expansion of UNAMIR's mandate would've required funds, and likely support from the United States, and no one wanted to take on that responsibility. I've heard it painted as a choice between trying to keep peace in Rwanda, or getting the US to stop supporting peacekeeping on the whole. If the US went in, the pains and costs would be so high that they'd effectively never participate again. The choice was already made: the UN was not going to get any more help in Rwanda.

After this surge in killing began, the Tutsi Rwandan Patriotic Front resumed its civil war against the Hutu government. However, this was not going to stop the genocide, which had already been planned. Killers of the Tutsis had target lists prepared, and names were read out over the radio, along with where they lived. The registering of Tutsis made it easy to track them down, and they were tracked down and killed before many even knew it was happening. Those who did know, and fled, were killed at checkpoints or caught. Everything from addresses to license plate numbers were broadcast. Within 3 weeks, the majority of the killings had already occurred, and the genocide had begun.

Some might say "this can't be a genocide, the Tutsi fought back", but keep in mind what genocide is. It's an attempt to eradicate an ethnic group. And that is what was attempted, and happened in large amounts. The Rwandan Patriotic Front (RPF) couldn't protect many of the Tutsis, especially not against the rapid advance.

Continued below.

Rwanda's was a German colony and then a Beglian colony after WW1. As other have discussed, the Hutu/Tutsi dynamic was exacerbated by colonial rule.

Interestingly, however Habyarimana and the Hutus were supported by the French in the 1990s (Mitterand had close relations with Habyarimana). For France, this area of influence in Central Africa is part of their claim to still be a 'global power'. France was openly hostile to the Tutsi-based Rwandan Patriotic Front (the current president comes from the RPF), and attempted to use its military and support the Hutu side in the Rwanda Civil War (the genocide was in some ways the 'final act' of the civil war). During the genocide, France famously evacuated ~1,500 westerners which was perceived as being 'not enough' during the crises. Much less French colonialism, then, but instead a desire to maintain some semblance of status of global power caused the French government to become associated with the side that committed a larger share of killings in 1994.

Source: Fate of Africa, Meredith

So I have a quick follow up question. Why are people so quick to blame Europeans for the Rwandan genocide, but blame the Germans for the Holocaust and the Japanese for the Rape of Namking? I would argue that the Treaty of Versailles set the stage for genocide in Germany, just as colonialism created what would be Imperial Japan. Why are these considered independent actors, but Rwanda is treated as almost not responsible for the action of the the Hutus?

Please note: This perspective isn't based on academia in so much as depictions I often see in the media and articles I have read about the genocide's anniversary.