- US envoy to United Nations blasts Syria, Russia, Iran over Aleppo crisis
- Samantha Power says Aleppo will join ranks with tragedies in Rwanda, Srebrenica, Halabja
(CNN)They are places synonymous with mass slaughter.
The names alone conjure images of unspeakable cruelty, unimaginable horror and unbelievable suffering.
Aleppo. Rwanda. Srebrenica. Halabja.
The US ambassador to the United Nations ticked off these names this week, as she launched a blistering attack on Syrian President Bashar al-Assad and his allies.
"Aleppo will join the ranks of those events in world history that define modern evil, that stain our conscience decades later," Samantha Power said at a UN Security Council emergency briefing on Syria on Tuesday. "Halabja, Rwanda, Srebrenica, and, now, Aleppo."
Power finds herself unable to stop another massacre under her watch, more than a decade after she won a Pulitzer for her critique of the world's failure to respond to genocides in her book: "A Problem from Hell: America in the Age of Genocide."
History is replete with examples of mass murders, and a world that had knowledge but failed to act.
"Power is clearly equating what is happening in Syria today with some of the widespread and systematic destruction of the civilian population in modern times ... egregious cases where the international community stood by and was witness to what happened," said Cameron Hudson, director of the Simon-Skjodt Center for Prevention of Genocide at the US Holocaust Memorial Museum.
There are several other documented cases of atrocities across the world: the actions of the Khmer Rouge and events in Darfur, Sudan, are just a few examples. In recent years the terror spread by ISIS has been added.
The word genocide is a legal term that came into existence after the Holocaust, when the "deaths were in a scale so unimaginable that a word needed to be invented to describe the nature of the crime," Hudson said. Six million Jews and millions of others were murdered in the Nazi camp system. Crimes against humanity is another term used to describe the widespread and systematic targeting of a civilian population, he said.
Here's a look back at some of the events named by Power.
Halabja, Northern Iraq. 1988
The horrific pictures of victims shocked the world.
The Organization for the Prohibition of Chemical Weapons calls it one of the most brutal and largest attacks using chemical weapons.
In March 1988, during the Iran-Iraq war, Saddam Hussein used chemical weapons against Iranian troops and civilians in the Kurdish city of Halabja in Northern Iraq.
More than 5,000 people died in 20 minutes and another 10,000 were severely injured in the attack, according to the US State Department.
The attack began with conventional shelling against the town that sent residents into their basement for protection, according to a report in the Council on Foreign Relations. Iraqi warplanes then dropped a mix of mustard gas, sarin and VS nerve agent.
Rich Brooks, one of CNN's longest-serving photojournalists, talked to CNN's Christiane Amanpour three years ago about his horrific experience.
"We weren't sure what we were going to see exactly," he said. "But what I remember vividly was entering the village and just how still and silent it was. Initially, we saw birds on the ground and then we saw cattle and sheep. And then we turned a corner into a street that was just full of bodies. And you've seen it before and the smell was overwhelming. ... They're seared into my mind. These were women, children, older people; they were not combatants and they were just dead where they fell. "
The attack helped tilt the war in Iraq's favor and bring Iran to the negotiating table.
In April 1994, Hutu extremists in Rwanda targeted minority ethnic Tutsis and moderate Hutus in a three-month killing spree that left an estimated 800,000 people dead. An estimated 300,000 of the genocide's victim were children.
Hutu attackers killed men, women and children, many of whom had been their neighbors before the conflict began. They burned down churches with hundreds or thousands of Tutsis inside, and in some cases they entered homes and slaughtered children and old people.
The violence was triggered by the death of President Juvenal Habyarimana, an ethnic Hutu, in a plane crash April 6, 1994.
The killings finally came to an end 100 days later, when Rwandan Patriotic Front troops, led by Paul Kagame, defeated the Hutu rebels and took control of the small East African country
Every year, beginning in April, Rwanda's government urges its citizens to "Kwibuka" -- the Rwandan word for "remember" -- in memory of the hundreds of thousands of lives lost during the country's genocide. Relatives of the victims and perpetrators alike are still searching for closure.
The July 11, 1995, massacre has been described as the worst atrocity on European soil since World War II. The breakup of the communist Yugoslavia generated savage bloodshed unseen on the continent.
The term "ethnic cleansing" became associated with Bosnia, when Serb forces loyal to their leader, Slobodan Milosevic, tried to carve out a separate state by forcing out part of the population.
The violence peaked with the assault on the tiny Muslim village of Srebrenica in July 1995.
In a five-day slaughter, up to 8,000 Muslims were systematically exterminated in what was described at the UN war crimes tribunal as "the triumph of evil."
Srebrenica had been designated a UN "safe area" in 1995, and that's why thousands of Bosnian Muslims had sought refuge in the spa town as the Bosnian Serb army marched toward them. The people were protected by just 100 lightly equipped Dutch peacekeepers, who proved no match for the advancing, heavily-armed Serb army. Thousands of men and boys as young as 10 were rounded up and murdered.
"For me, the war and what I witnessed changed everything. I saw the very best and worst of humanity," writes CNN Chief International Correspondent Christiane Amanpour.
The man who was regarded as the chief architect of the carnage, Milosevic, died in custody at the Hague 10 years ago, while on trial for war crimes.
His deputy, Bosnian Serb leader Radovan Karadzic, was sentenced to 40 years in prison.
The war crimes trial of Bosnian Serb military chief Ratko Mladic ended Thursday, and a verdict should be out within a year.
Aleppo, Syria, 2016
Turkey's Minister for EU Affairs compares the situation in eastern Aleppo to Srebrenica, when the world failed to stop the genocide in the former Yugoslavia.
"Sadly, the people in Aleppo are facing a major genocide in front of the eyes of the whole world and modern institutions," Omer Celik said Thursday.
The Syrian war began as peaceful pro-democracy protests that erupted as part of the 2011 Arab Spring uprisings. It escalated to a crackdown by the Syrian regime of President Bashar al-Assad. Hundreds of thousands of people have been killed, and millions displaced.
The city of Aleppo was once Syria's cultural center, economic powerhouse and a bustling metropolis of more than 2 million people.
Today it is a devastated war zone. Government planes bombarded the rebel-held eastern part of the city and choked off the supply of food, fuel and other necessities, essentially cutting it off from the outside world.
As government forces surround the city this week, activists said anyone with links to the rebels who seized control of the enclave in 2012 was being hunted down. The United Nations said at least 82 civilians were shot in their homes and streets as government forces advanced this week.
"Aleppo is being destroyed by the silence of Arabs and the entire world," is the translated quote from one of the top Twitter worldwide trends.
Evacuations were under way Thursday, but if the regime does take control of Aleppo, it would mark a turning point in the civil war.
"It took 4,000 years, hundreds of generations, to build Aleppo," Jan Egeland, special adviser to the United Nations special envoy for Syria, said Thursday. "One generation managed to tear it down in four years."
"There was this feeling during the Holocaust -- if only we had known more, more could have been done to stop it," said Hudson, with the US Holocaust museum.
"That assumption is completely undermined by events of last week -- we know what is happening in Aleppo and when it is happening in real time -- it is being delivered on our computers and cell phones, and that hasn't provoked any kind of response from the world."