The Worst Day in Human History:  January 23, 1556

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Podcast Transcript

Humanity has seen a lot of bad things throughout its history. There have been horrific wars, natural disasters, and pandemics that have killed millions of people. 

Many of these awful events were awful over a period of weeks, months, or years. 

It raises the question, what was the worst single day in history? What day was the absolute worst when all the horrible things were punctuated in one twenty-four-hour period?

Learn more about the worst days in history and arguably the one that was the very worst on this episode of Everything Everywhere Daily.


This episode began with a very simple question: what was the worst day in world history? 

This question is a much more difficult question to answer than you might think. 

I fully admit up front that the topic of this episode is a bit morbid. I’m going to be talking about the deaths of many tens and hundreds of thousands of people. However, it puts into perspective just how bad things can get over the scope of history.

History is rife with horrible events, and almost all of these events, because of their scale and when they occurred, have a great deal of uncertainty regarding just how bad it was. 

Recording keeping is often poor; historians, particularly ancient historians, often exaggerated the result of battles and disasters. Trying to determine the truth from ancient sources is often difficult, if not impossible. 


It isn’t just ancient sources. Modern disasters can have a great deal of ambiguity surrounding the number of deaths as some people simply disappear or the numbers are so great that they can’t be accurately measured.

So, if we are going to tackle this question of what is the worst day in history, we should try to set some parameters. 

The easiest way to measure what the worst day was would simply be to try and determine what day saw the greatest loss of human life. 

This sounds simple, but it isn’t. 

Every day, people are born, and people die. The Earth currently has about 8.2 billion people. Every single day, about 175,000 people die on average across the planet.

Most of this, of course, isn’t the result of disasters, it is just the baseline of normal human demographics.

Prior to the explosion in population, which mainly began in the 19th century, the global population was believed to have been around 500 million people for most of history. 

If we take the current number of daily deaths and normalize it for the population thousands of years ago, you’d have about 10,000 deaths per day on average. However, this doesn’t take into consideration that there were more births and more deaths due to a lower life expectancy. 

So, if we conservatively increase the number by 50%, that would be 15,000 per day. 

So, even if we normalize it over time, the worst day in history would have to be greater than 15,000 in ancient history and probably more than 170,000 today. 

That means that many truly traumatic events like 9/11 or Pearl Harbor wouldn’t come close to making the cut. They were certainly tragic events, but as we’ll see, they don’t even come close to being the worst days in history. 

I might as well start by addressing one of the biggest historical causes of death: disease. Over time, diseases and pandemics have been responsible for more deaths than war and natural disasters. However, they also tend to take place over time. 

The Black Death may have killed 50 million people over a seven-year period. Given its most liberal estimate for the number killed during the Black Death, you get at most 19,500 people per day. There would be some variation in that number, so there was certainly one day that was the worst, but we have no idea what that day might have been. 

Likewise, the Great Dying of the Americas after the arrival of Europeans may have killed as many as 100 million people from various diseases over the course of a century. Again, an enormous number in total, but spread out over a long time. 

The Spanish Influenza may have killed as many as 40 million people in 1918 and 1919, which would average to about 55,000 dead per da, assuming the highest estimates. 

Because of the nature of pandemics, despite being some of the worst events in history, it would be almost impossible for them to be responsible for the worst single day in history. 

For the same reason, famines are unlikely to be the cause of the single worst day in history either, even though they, too, have been responsible for great losses of life.

Wars and great battles might be a good candidate for having caused the worst day in history.  

The Battle of Cannae, which took place on August 2, 216 BC, during the Second Punic War, saw the greatest single defeat of a Roman army, a subject that I’ve covered in a previous episode. 

Estimates of the total number of killed during the battle, almost all of which were Roman, are between 50,000 and 70,000.

Ancient battles such as these were able to have such large single-day death tolls because the battles took place in smaller areas with a higher density of soldiers. Most battles were also fought in a single day.

Many, many ancient battles had death tolls into the tens of thousands and sieges that went into the hundreds of thousands, but those took weeks or months. 

So, to be generous, the worst one-day battle in the ancient world we can probably cap at 100,000, and that includes sieges.

However, there was a group in the 13th century that took death to a level that had never been seen before: The Mongols. 

The total number of people killed outright by the Mongols in battles, sieges, and the sacking of major cities is estimated to be between 50 and 100 million people. The reduction in the population in Asia during this period actually shows up in the ice core record. 

In a previous episode, I covered the Siege of Baghdad in 1258. When the city surrendered and the Mongols entered on February 13, they spared no one. 

Estimates as to the number of dead range from 200,000 to one million. The destruction took several days, but February 13, 1258, has to rank as one of the worst days in history. It is more likely that the real number is closer to the lower estimate, probably 200,000 to 400,000 killed in a single day. 

This wasn’t the first time the Mongols had done this. In April of 1221, the Mongolos exterminated every single person in the city of Nishapur. They beheaded everyone, including all of the animals. 

Here, too, the estimates vary widely from a few hundred thousand to as many as 1.7 million. It is highly unlikely that it would even be possible to behead that many people in a single day, and it is most likely that the higher estimates include the entire Khwarazmian Empire in what is today Iran. 

What about modern wars? The wars of the 20th century had far more combatants compared to any other wars, along with greater civilian deaths. 

At the start of the Battle of the Frontiers on August 22, 1914, at the very start of the First World War, the French lost an estimated 27,000 troops. This and the Battle of the Somme were two of the worst single days of the war, which was actually less the same ancient battles. The devastation of the war came from the fact that so many died every single day for years. 

The worst battle of the Second World War was Stalingrad. An estimated 1.2 to 2.5 million people were killed, making it the worst battle in human history. 

However, the worst days of the fighting may have only seen ten or twenty thousand dead as the siege lasted over six months. 

The same is true for the Siege of Leningrad, which had a death toll almost as high. 

I’m sure many of you have been thinking the exact same thing since the very start of this episode. The worst day of the Second World War had to be the day the atomic bombs were dropped on Hiroshima and Nagasaki. 

You wouldn’t be wrong. Both of those days were very bad. An estimated 80,000 people were killed in Hiroshima instantly, and another 40,000 were killed instantly in Nagasaki. In both cities, many more were killed in the days and weeks that followed.

However, believe it or not, the dropping of the atomic bomb was not the worst day of the war. That took place on March 15, 1945, when around 100,000 civilians burned alive in firebombing raids conducted by the U.S. on Tokyo.

So, the worst day in history due to military action was probably the slaughter by the Mongols in either Baghdad or Nishapur, although we don’t know the exact numbers. It was probably in the low to mid hundreds of thousands.

That leaves us with natural disasters. 

As bad as war is, and is pretty bad, it is hard to beat the destructive power of an earthquake, tsunami, flood, or volcano. 

It should come as no surprise that the worst natural disasters in human history have mostly occurred in the 20th century. This is simply due to population levels. 

A similar disaster centuries earlier wouldn’t have affected as many people.

Over just the last 60 years, there have been at least three natural disasters that have killed close to or more than a quarter million people in a single day. 

On December 26, 2004, the Indian Ocean tsunami was estimated to have killed as many as 230,000 people, much of that within just a few hours. 

On July 28, 1976, an estimated 242,000 people were killed in one day from the Tangshan Earthquake in China. 

Finally, on November 13, 1970, an estimated 300,000 to 500,000 people were killed by the Bhola Cyclone in Bangladesh due to a massive storm surge.

An estimated 4,000,000 people were killed by flooding along the Yangtze and Huai Rivers over the course of two months. 

All of these things I’ve listed to this point were horrible and tragic. Yet none of them can qualify as the worst day in human history. 

Most of the people who have written on this subject have all come to the same conclusion. 

The worst day in human history was January 23, 1556, in the region around Shaanxi, China.

An earthquake that measured approximately 8.0 on the Richter scale hit the region. 8.0 is a very powerful earthquake, but it is far from the strongest in history. 

The earthquake struck one of the most populated areas in China at the time, with densely packed cities and villages spread across the fertile Wei River Valley. 

This region was home to millions, many of whom lived in loess cave dwellings known as yaodongs. These structures were carved directly into the soft, compacted soil, which, while insulating against temperature extremes, became a deadly trap when the earth began to shake. The earthquake’s violent tremors caused widespread collapses, instantly burying thousands of people inside their homes.

Beyond the immediate destruction of homes and buildings, the nature of the terrain contributed significantly to the high death toll. The Wei River Basin and surrounding areas were composed of loess, a type of fine, wind-blown silt that is highly prone to landslides when disturbed. 

The earthquake triggered massive landslides, wiping out entire villages in an instant. Ground fissures and soil liquefaction further compounded the devastation, making rescue efforts nearly impossible in the aftermath.

Entire cities crumbled as walls collapsed and roofs caved in, crushing those inside. The urban centers suffered immensely as government buildings, temples, and marketplaces were reduced to rubble.

Many of those who managed to survive the initial quake were killed in fires or froze to death that evening. 

An estimated 833,000 people were killed in a single day. 

Not only was this the single worst day in human history in terms of total lives lost, but the population of the Earth was only around 500 million people at this time, so as a percentage of the population, it was even greater.

There is one other event I should probably mention, but there is very little we know about it. The only thing we know comes from the geologic and genetic record. 

About 74,000 years ago, Mount Toba in Indonesia exploded. It was an eruption unlike any that has ever been seen in recorded human history. 

In a previous episode, I covered the Mount Tambora eruption in 1815 which caused the year without a summer.  The Tambora eruption sent over 80 cubic kilometers of ejecta into the atmosphere. 

By comparison, the Toba eruption sent 2,800 cubic kilometers into the atmosphere, the equivalent of 35 Tamobra eruptions. 

It almost wiped out humanity. We have no idea what the total population was at the time or how many people died, but we do know that there was a genetic bottleneck that occurred in humanity at the same time as the Toba Eruption. 

Humanity has seen a lot of bad days due to natural disasters, war, disease, and famine, and it is sad to say we will probably have more. 

However, as far as we know, there has never been a day as bad as January 23, 1556.