The first hour of Monday night's Republican convention session has been dominated by discussions of Benghazi — the September 11, 2012 terrorist attack in Libya that claimed the lives of Ambassador Chris Stevens and three other Americans. The argument being made is that Hillary Clinton is responsible for the deaths of these four, and for covering up the truth about the attacks.

"I blame Hillary Clinton personally for the death of my son. Personally," Pat Smith, mother of State Department officer Sean Smith, said.

Smith's speech was visceral, raw, and important to empathize with. But no official inquest into Benghazi — and there have been many — has found evidence that Clinton is personally responsible for the events of that night.

Take the House Select Committee on Benghazi report, the most recent investigation led by Republicans whose findings were released in late June. After two years of investigation and millions of dollars spent, the report has uncovered no new evidence of wrongdoing by either the Obama administration or Hillary Clinton.

"Ending one of the longest, costliest and most bitterly partisan congressional investigations in history, the House Select Committee on Benghazi issued its final report on Tuesday, finding no new evidence of culpability or wrongdoing by Hillary Clinton in the 2012 attacks in Libya that left four Americans dead," David Herszenhorn reported in the New York Times after its release.

This, perhaps, should be unsurprising: The Benghazi attack has been one of the most litigated events of the entire Obama administration. It's prompted nine separate investigations and a series of political controversies so severe they ended Susan Rice's bid to become secretary of state, indirectly led to Clinton's private email scandal, and, in a strange turn, damaged House Majority Leader Kevin McCarthy, a Republican who supported the investigations.

To understand why Republicans are still devoting so much time to it on such a critical convention night, you need to understand all of this history — and of course, what we know about the attack itself. What follows is a clear, simple guide to Benghazi — from the attack itself to the scandals that followed to the ways it's still shaping American politics today, including in the report released today.

1) What is the Benghazi controversy?

The controversy has centered on Republican accusations that the Obama administration did not take heed of intelligence warnings before the attack, that during the attack it refused to call in available military support, and that after the attack it deliberately covered up what had happened.

Repeated independent investigations have disproven all of these allegations. But Republicans have continued to push them, insisting that these failures go all the way to the top, personally involving President Obama and then-Secretary of State Hillary Clinton.

"Everybody thought Hillary Clinton was unbeatable, right? But we put together a Benghazi special committee."

But the administration did make two mistakes. First, the State Department failed to provide sufficient security at Benghazi, which an internal review blamed on "systemic failures" at the department’s "senior levels." Second, Obama administration officials initially mischaracterized how the attack began (more on this below), but investigations found they were honestly relaying the CIA's assessments, not deliberately lying, as Republicans charged.

The investigations have had real political ramifications. The House Select Committee on Benghazi, created by Speaker of the House John Boehner in 2014, found the first documented evidence that Hillary Clinton used unauthorized private email servers for State Department business, which became a major scandal.

One of the select committee's biggest casualties has been a Republican who backed it: Kevin McCarthy. He was running to be the new speaker of the House when, last year, he seemed to admit something Republicans had long denied: that the taxpayer-funded investigation was really a partisan exercise to hurt Hillary Clinton's political career.

"Everybody thought Hillary Clinton was unbeatable, right? But we put together a Benghazi special committee, a select committee, what are her numbers today? Her numbers are dropping," McCarthy said on Fox News. About a week later, amid controversy over his comments, McCarthy dropped out of the race to be speaker.

These comments seem more foolish now that the investigation's report has been released, finding no new evidence of wrongdoing on Clinton's behalf.

2) What actually happened in Benghazi on September 11, 2012?

Before September 11, 2012: In 2011, Libya's government is toppled by a popular uprising and Western intervention. The civil war has ended by September 2012, but with the government gone, much of the country was lawless, dominated by militias.

Day of September 11, 2012: US Ambassador to Libya Chris Stevens visits Benghazi.

Elsewhere, demonstrators gather outside US diplomatic buildings in a number of Muslim-majority countries, even climbing the wall surrounding the US Embassy in Cairo, to protest The Innocence of Muslims, an amateur anti-Islam film, clips of which had been recently translated into Arabic by Egyptian media.

Between 8:30 and 9 pm, Benghazi time: Members of local Islamist militias in Benghazi decide, somewhat spontaneously, to seize on the day's protests and attack the US diplomatic outpost there, assembling around its gates.

9:42 pm: The attackers breach the mission's gates, easily overpowering the small American and Libyan security detachments. After gaining access to the building, they set fire to it.

10 pm: American security attempts to evacuate Ambassador Stevens and State Department Information Management Officer Sean Smith, but loses them both in the smoke. A diplomatic security agent tries again to locate them but is forced to retreat to the roof of the building after suffering severe smoke inhalation.

10:10 pm: A CIA support team arrives at the mission to defend the diplomatic staff and assist with the evacuation.

11:15 pm: After a final search for Stevens fails to find him, the combined American forces leave for the CIA Annex (about a mile away) under heavy fire. They arrive 15 minutes later.

11:56 pm: Militants follow them and attack the CIA annex with rifles and rocket-propelled grenades.

Around 1 am: Locals find Stevens and rush him to a nearby hospital, where soon after he dies of smoke inhalation. Smith also dies of the same cause.

5:15 am, September 12: The annex is hit by mortar fire for 11 minutes. Diplomatic security agents Tyrone Woods and Glen Doherty are killed attempting to return fire, and another unnamed agent is seriously wounded. The severity of the mortar attack convinces the chief of base that they need to abandon Benghazi altogether.

6 am: Local Libyan forces finally arrive and protect the Americans during their drive to the airport and exit from the city.

3) Who were the attackers, and why did they do it?

The attackers were an informal group of Islamist fighters from an assortment of local Libyan militias; a number came from an extremist group called Ansar al-Sharia, and a few had ties to al-Qaeda.

But this was no carefully preplanned attack. It was much more spontaneous — and in some ways a product of Libya's chaos.

In March 2011, Libya was divided by civil war. Rebels held the east, with a de facto capital in Benghazi, and Muammar Qaddafi's forces held the west. When Qaddafi sent tanks to retake Benghazi, the US and its NATO allies intervened with air and missile strikes against him. As the war raged on, NATO provided air support, but the ground war was fought by Libyan rebels, many organized into volunteer militias.

When Qaddafi fell, the government collapsed along with him, and what remained of the military was too weak to retake control of the country. Much of Libya fell into chaos, with militias dominating its cities and neighborhoods. Some of those militias were Islamist extremists.

"The nature of the attacks suggested they did not involve significant preplanning"

By the time Stevens arrived in Benghazi, the city was lousy with militia fighters. According to then-acting CIA Director Michael Morell, some militants in the city heard about how a mob had successfully scaled the walls of the Cairo Embassy earlier on September 11 and, spur of the moment, "decided to make some trouble of their own."

"The nature of the attacks suggested they did not involve significant pre-planning," Morell wrote to Sen. Dianne Feinstein in 2013, summing up the consensus among US intel agencies. Instead, it was a haphazard alliance of convenience between individual militiamen — a kind of attack made possible by the total chaos that prevailed in Benghazi after Qaddafi was toppled.

4) Could the Obama administration have stopped the attack?

The attack was too spontaneous, for the reasons described above, for US intelligence to see this specific incident coming. But what about once it had begun?

One of the biggest myths about Benghazi is that the US had military assets in range — but refused to deploy them. "Military personnel were ready, willing, and able, and within proximity, but the Pentagon told them they had no authority and to stand down," Rep. Jason Chaffetz said in 2013.

This is flatly false, as the House Select Committee's report explains: "The assets ultimately deployed by the Defense Department in response to the Benghazi attacks were not positioned to arrive before the final lethal attack."

However, we've known this for some time. The bipartisan Senate Intelligence report, perhaps the most comprehensive and balanced review of the attack, found that "there were no US military resources in position to intervene in short order in Benghazi to help defend the Temporary Mission Facility and its Annex."

Still, it was no secret that Benghazi was dangerous. In retrospect, it's clear that the US mission there was too lightly guarded and fortified, and Stevens himself had requested more security. How did this happen?

The problem, according to an internal State Department review, was essentially bureaucratic. Two State Department bureaus, Diplomatic Security and Near Eastern Affairs, had nominal authority — but no one person or bureau had point on Benghazi security. Both Diplomatic Security and Near Eastern Affairs made piecemeal improvements to security, but neither did enough.

The mission also had a confusing legal status. It wasn't an embassy or even an official consulate; it was so off-book that the Libyan government was never officially notified of its existence. This put the mission outside the normal State Department procedures used to allocate security funding and personnel.

5) What's the "talking points" controversy? Did the White House hide the truth about Benghazi?

The "talking points" in question are the official administration talking points, from just after the attack, on how to describe what had happened. Susan Rice, then the US ambassador to the UN, used these talking points when she appeared on Sunday talk shows that week.

Rice claimed, in her appearances, that the attack had grown out of a spontaneous protest against the anti-Islam film Innocence of Muslims. She didn't make this up; it was the CIA's assessment at the time.

But this claim turned out to be wrong. While some of the attackers really were incensed by the film, closed circuit footage from the diplomatic building showed that there was no protest.

In the subsequent "talking points" controversy, Republicans accused the White House of making up the "spontaneous protest" claim in order to cover up their failure or downplay the role of terrorism. They also accused the administration of inappropriately manipulating the talking points during internal discussions.

Congressional Republicans spent countless hours looking into the talking points. Detailed dissections of the talking points, like this one from the Weekly Standard's Steven Hayes, appeared all over right-wing media.

But the CIA did in fact believe, in those first few days, that the attack had grown from a protest against the anti-Islam film. Then-CIA Deputy Director Mike Morrell — and not any White House official — actually removed a reference to al-Qaeda from an early draft of the talking points.

Now, the CIA assessment was badly flawed. The House Select Committee report documented a number of errors in it: for example, it cited a news article from September 4 as evidence of a protest happening on September 11.

But these were the CIA's errors, not the White House's. While the talking points Susan Rice used were incorrect, this was an honest CIA error made in the first days after the incident, and not a deliberate White House cover-up. There is no evidence of inappropriate White House tampering. Former CIA Director David Petraeus said in Senate testimony on November 16, 2012, "They went through the normal process that talking points — unclassified public talking points — go through."

Still, the incident made Rice so controversial that she was forced to withdraw her name from consideration to become secretary of state. Continued Republican interest in the talking points also seems to have played a role in Boehner's decision to create the select committee in May 2014 — the body that uncovered, somewhat accidentally, the Clinton email scandal.

6) What have the investigations into Benghazi found?

Nine different bodies have investigated Benghazi: the State Department's Accountability Review Board and eight separate congressional committees or staff reports. With the select committee's reports in, all of them have now completed investigations. Each has identified problems with the way the incident was handled, but none have uncovered real evidence of an administration cover-up or failure to properly respond to the attacks.

7) So many investigations! Can we take a music break?

Here's "Cover Up (The Benghazi Song)," a 100 percent real — and seemingly earnest — protest anthem by the Barry Fasman Experience:

This song is pretty ridiculous, but it's emblematic of the way that Benghazi has become a kind of folk obsession among the conservative rank-and-file. You can buy Benghazi T-shirts, throw pillows, and mugs. This now-infamous acrostic tweet may best capture the Benghazi hysteria:

B A R A C k E Negligence G H @HillaryClinton A is for ABANDONMENT Z I #BENGHAZI B E N G HELL A Z Incompetence @SpeakerBoehner — SpreadButter (@SpreadButter) October 18, 2013

Probably the best encapsulation of liberal exasperation with all this is Chris Hayes's MSNBC segment on the "two Benghazis." Hayes argues that there's "the real Benghazi" — the actual city in Libya, a place where things of real concern like the 9/11/12 attack happen — and "#Benghazi," which he defines as "the world of online conspiracy theorists, Twitter trolls, and Facebook right-wingers."

8) If there's long been no evidence of a cover-up or wrongdoing, why did House Republicans just release another report on this?

Republicans' interest in Benghazi isn't just cynical politics (although there is for sure some of that). Conservatives have long seen Obama as a feckless, incompetent liar — the idea that he failed to prevent a terrorist attack, then covered it up, fits with their preexisting beliefs. The fact that independent reporting vindicated the administration didn't help, as conservatives see the mainstream media as hopelessly in the tank for the president. So long as conservative leaders argued there's a scandal here, some Republicans kept believing that more investigations were necessary. Hence the select committee.

Individual Republicans also had incentives to pursue this. Benghazi became such a huge issue among the conservative base that pushing the issue, at least in theory, should translate into more fundraising dollars and more support from the base in Republicans' reelection bid. Conversely, any Republican who tried to downplay Benghazi risked a conservative backlash. So even skeptical Republicans had an incentive to endorse more investigations into Benghazi.

But there is no hiding the fact that this is also about transparent partisan politics. Republicans have ignored repeated investigations debunking their allegations and have consistently tried to tie the incident to Obama and Clinton personally. Whether the select committee's inability to link the attack to failures by either will bring the focus on Benghazi to an end remains to be seen.

Ironically, the Benghazi attack does raise one very big issue that's getting relatively little GOP attention: what it says about the US intervention in Libya, which contributed to the chaos in which Stevens was killed. Was the intervention a mistake? Should the US have never intervened, or only intervened if it also planned to do the necessary work of rebuilding Libya's government?

But GOP orthodoxy is that Obama is too cautious in the face of foreign threats — making it hard for Republicans to criticize him for being too aggressive in Libya. So instead of talking about the basic wisdom of the Libya war, they focus on "weakness" in the face of terrorism and an alleged cover-up.

9) What does this have to do with the Hillary Clinton email scandal and the House speaker election?

This all dates back to then-Speaker of the House John Boehner setting up the House Select Committee in May 2014.

The committee, for its investigation, asked the State Department to turn over emails Clinton had sent to her aides about the attack. Some of those emails turned out to have been sent from Clinton's private email account — which, according to the New York Times, is how Clinton's use of a private email server for official State Department business first came to light. That's become a big campaign scandal for her, to somewhat understate things.

Then in a September 2015 appearance on Fox News, House Majority Leader Kevin McCarthy seemed to admit something that Republicans aren't supposed to say — that the real purpose of the Benghazi Select Committee is to hurt Clinton's campaign:

Everybody thought Hillary Clinton was unbeatable, right? But we put together a Benghazi special committee. A select committee. What are her numbers today? Her numbers are dropping. Why? Because she’s untrustable. But no one would have known that any of that had happened had we not fought to make that happen.

This allowed Clinton to dismiss the email scandal, and the Benghazi issue in general, as a trumped-up partisan sideshow. Reporting on the emails has slowed since — though that might change if Trump makes a big deal out of them in the general.

But McCarthy's gaffe appears to have really hurt him.

McCarthy had been running to replace Boehner as speaker, and was the overwhelming favorite. But the Benghazi gaffe helped fuel an anti-McCarthy rebellion among the House's most conservative members. McCarthy withdrew from the speaker race on October 8, citing the Benghazi comments as a reason for dropping out. That's why Paul Ryan, not McCarthy, is the speaker of the House today.

We'll now see if, after the House report lands as a dud, this issue loses its political potency. Given that Hillary Clinton is the Democratic nominee, and currently leading Donald Trump by wide margins, there's a chance Republicans may still keep bringing it up.

Benghazi, the attack and the scandal, explained