"What begins with the failure to uphold the dignity of one life, all too often ends with the calamity of entire nations", remarked Kofi Annan once.
It is a sentiment that was all too true for the 20th century as genocides and mass killings on a scale never thought possible before occurred throughout the world.
Here are four of the most infamous genocides of the 20th century which shook humanity to its core and changed the course of history forever.
The Holocaust: The horrors of a world war
One of the greatest human calamities that occurred in Nazi Germany during WWII was the Holocaust.
The nationalist German leader Adolf Hitler rose to prominence spewing hatred against Jews, Slavs, and others.
He promised the Germans a great future through the 'purification' of their 'superior' Aryan race and quickly moved to turn his rhetoric into action once he became the Chancellor of Germany.
Millions of people were killed through starvation, forced labour, rape, systemic killing, and medical experimentation as the German Army marched through the heart of Europe.
The early years of WWII (the early 1940s) saw the Germans annihilate millions for 'Purification of the Aryan race' and 'Lebensraum' (Living space for Germans).
Nearly six million Jews were murdered during the Holocaust; along with 11 million others including Slavs such as Russians, Ukrainians, and Poles before the allied forces finally liberated the concentration camps in 1945.
Few of the surviving perpetrators were tried at the Nuremberg Trials and subsequently punished, Hitler himself committed suicide before the German surrender in 1945.
The Holocaust also reignited the debate for a Jewish homeland which later materialised into the state of Israel.
Later, the Israeli secret service, Mossad, also tracked down and apprehended some of the most notorious Nazi criminals who actively took part in the genocide.
The subsequent German governments have apologised for the horrific crimes during the Holocaust.
The western part of divided Germany paid an equivalent of $1.5 billion to the state of Israel as reparation and helped the resettlement of 500,000 Jews in the 1950s.
The Holocaust left a deep mark on today's world. It has forever changed how the world looks at anti-Semitism, fascism, and 'racial purity'.
The Genocide in Bangladesh: The cost of freedom
1947 saw the bifurcation of British India into two distinct parts, one of which was Pakistan, a state which was inhabited by various groups who came from vastly different cultural backgrounds and territories that were placed on both sides of India.
Racial hatred and the refusal to respect the democratic will of the people led the military junta of Pakistan to execute 'Operation Searchlight' on the Eastern wing of the country killing thousands of innocent Bangalis including politicians, teachers, students as well as people from other walks of life.
The military leader, General Yahya Khan infamously declared, "Kill three million of them and the rest will eat out of our hands!"
Soon Operation Searchlight expanded into larger operations and the Pakistani forces massacred millions of people in the next nine months before the Bangali freedom fighters (better known as the Muktibahini), aided by the Indian Army defeated them, liberating the land of the Bangalis - Bangladesh.
The genocide began on March 25, 1971, and continued till the occupying Army's surrender on December 16.
The nine-month carnage by the Pakistani forces resulted in mass executions, indiscriminate shootings, arson, looting, and rape of over 200,000 women as well as the flight of 10 million refugees into neighbouring India.
Though Bangladesh had tried a few war criminals, most of the perpetrators and collaborators went free. 93,000 Pakistani troops were freed by India in the mid-1970s.
Though Yahya Khan faced a tormenting fate as he was stripped of all honours and detained until he drank himself to death, most of the perpetrators never faced any consequences for their actions except for their brief internment in India.
The Pakistani government continues to deny the genocide to this day and remains unapologetic about the horror it inflicted on Bangladesh in 1971.
On the other hand, the genocide has forever changed Bangladesh.
The weaponisation of rhetoric, fundamentalism, and racism has taught Bangladesh to be a more inclusive society than East Pakistan or for that matter, the whole of Pakistan ever was.
It has influenced the rest of the world as well.
Three million dead bodies of the 1971 Bangladesh genocide continue to remind the world of the horrendous cost of freedom and the true extent of evil bigotry can inflict on humans.
The Cambodian Genocide: Ashes of a misguided revolution
Pol Pot, the leader of the Communist Party of Kampuchea, engaged in a bitter struggle to turn Cambodia into an egalitarian socialist state for years before finally succeeding in 1976 when he became the Prime Minister overthrowing the previous government.
His utopian vision of Cambodia soon turned the country into hell as he forced millions of people to relocate to the rural areas for farming to create an egalitarian agrarian society.
People's lives began to be controlled as the governing body, better known as the Khmer Rouge, made people live according to their version of egalitarianism through actions such as forcing the same black clothing on everyone and killing anyone who dared to complain.
Supported by both China and the United States, Pol Pot moved on to exterminate all of his 'perceived enemies' in his newly established one-party communist state.
Soon anti-Muslim, Anti-Vietnamese and other intolerant fanatic ideals began to seep into the new regime.
Thus began a genocide that continued for four years before the invading Vietnamese troops finally toppled the Khmer Rouge regime in 1979.
The genocide claimed the lives of close to three million people which was roughly a quarter of Cambodia's population at the time.
Dissenting people, officials of the previous regime, Muslims, Buddhists, Vietnamese Cambodians as well as numerous others were taken into concentration camps, experimented on, forced to do hard labour and killed.
Mass graves filled the country and people were killed by the thousands.
The condition became so severe that the security forces began killing people with pickaxes to save bullets!
The Documentation Centre of Cambodia has counted more than 23,000 mass graves.
One description by Ben Kiernan's 'The Pol Pot Regime' vividly captures the horror where the author describes how 20,000 prisoners were taken into Tuol Sleng (termed as Security Prison 21 by the regime) and only seven of them came out alive.
The Vietnamese invasion stopped the Khmer Rouge in 1979 and the subsequent governments tried some of the perpetrators though Pol Pot managed to flee the new authority and escape persecution.
A sick and defeated man on the run, Pol Pot was betrayed by his own men and imprisoned in his final days, eventually dying in 1998.
Cambodia as well as the world solemnly remembers the victims of the Khmer Rouge's atrocities.
The bones and skulls found in thousands of mass graves across Cambodia stand as a stark reminder for humanity of what an extremist and bigoted mindset with unchecked power can do in the pursuit of its own version of 'egalitarianism'.
The Rwandan Genocide: The 100-day carnage against humanity
The Hutus and the Tutsis, two ethnic groups of Rwanda, have been at odds with each other for decades.
Dominated by the Hutu ethnic group, President Juvénal Habyarimana's government made a peace deal with the rebel group called 'Rwandan Patriotic Front' (RPF) (which was made up of minority Tutsi people) ending decades of ethnic tensions in the early 1990s.
Yet the peace accord fell through once the president got killed and the extremist Hutus took over.
A systematic killing campaign began against the Tutsis and moderate Hutus that killed nearly 500,000 to 600,000 people within 100 days, shocking the global community before the RPF finally overthrew the regime and forced the Hutu extremists out of the country.
The world stood horrified as international media outlets such as the BBC, AP, and others began uncovering the true extent of the killings.
The genocide unleased the darker side of the human psyche as husbands who killed their Tutsi wives claimed that they would have been killed if they did not do it.
Nuns and priests were also later convicted for killing Tutsi people seeking refuge at the church.
Mass rapes and killings of the Rwandan minority population shocked humanity to its core.
Later, the newly established RPF-led Rwandan government started a retaliatory war against Hutus prolonging the violence.
The genocide and subsequent reprisals forced millions of refugees into the Democratic Republic of Congo and caused indescribable suffering to many.
Sexually transmitted diseases, unusable infrastructure, broken families, and horrors of the genocide have changed Rwanda forever.
The global community has also been heavily criticised for not responding quickly to the genocide.
As the global civilisation progresses further, we must remember horrific events such as the Rwandan genocide to avoid a repeat of such heinous crime ever again because as the novelist George Santayana once said,
"Those who cannot remember the past are condemned to repeat it".