In the mid-14th century, conditions weren’t exactly ideal for living in. There was a population crisis with jam-packed cities and hundreds of people roaming the streets. There was poor sanity, and the towns were overloaded with filth. People threw trash out of their windows and onto the streets, which functioned more like open sewers. With this, political and economic friction had grown and was at an all-time high. These living conditions favoured the welcome of a lethal guest who would soon sweep out nearly 200 million souls from the mortal realm. The event came to be known as "The Great Mortality" or "The Black Death."

Every disease needs a lair to grow in. Though the exact location of the plague’s origin hasn’t been pinpointed yet, experts argue that it probably originated somewhere in the Mongolian plains or in the Issyk-Kul Lake, one of the deepest lakes in the world. But the region lying between the Eurasian Steppe and the Gobi Desert has been hotly debated as well.

Nevertheless, the danger remained unnoticed for a long period of time by the rest of the world. Since its lair was isolated from human settlements, it grew and evolved into something completely horrendous.

Yersinia Pestis [bacterium of the Black Plague] had the most unexpected carriers, which made it easier to expand its domain across the globe. Rattus Rattus and Xenopsylla Cheopis were two of them.

How it all began:

By the mid-14th century, the Mongolian plains were unified by the Pax Mongolica. Countless silk roads were set up that ran across the land, like the veins spread across the lamina of a leaf. Many trade stations and oasis stopping points were established, attracting traders from far lands to come and try their luck in the region. Along with this, "The Riders of the Yam" (a famous Mongolian pony express) were created to help with the trade in the region.

The sudden exposure of humans helped the plague enter new lands.

There were several other factors which contributed to the spread, one of them being the friction between the Mongolians and the Genoese.

Back in the mid-13th century, the climate was ideal and high-yielding crops kept the population well fed. This helped it increase and expand the human domain to new lands. Europe managed to yield a population of 75-80 million citizens.

Times changed quickly and the weather worsened. Countless ecological disasters hit the mortal realm. People struggled through the harsh droughts and floods, barely managing to survive. Earthquakes shook the earth and demolished settlements. This was a hard period; These disasters didn’t just cause suffering, they caused something much worse, something that had the potential to cause a pandemic. It caused massive rat migrations.

Other events:

The fall of the Roman Empire in the 13th century paved the way for Italian cities such as Venice, Genoa, and Florence to grow strong economies and "modernise" their regions. Markets flourished, and the city's domains expanded. On the other hand, the region of Caffa remained under-developed and was often described by travellers as a "primitive fishing village". The world was changing, and the empire grew frustrated with Caffa’s lack of urbanisation. They wanted the city to be a simulacrum of Venice and Florence.

On reaching Constantinople in 1204, the Fourth Crusade declared a testament with its 95th acquisition, stating the city to "Expand or Die!". Thus, in 1266, the Genoese arrived on the land and started the tiresome work of "modernising" Caffa.

With the efforts of the Genoese, hamlets grew into towns and shops grew into bustling markets. Quaint buildings were established, which stretched far into the sky, and aesthetic streets and roads were set up for the people. Countless services were established in the region as well, dedicated to providing utilities. Caffa had several docks built near her warm waters. She was the proud owner of over 200 ships.

The location was an ideal spot for trade. The silk routes ran up in the North. The Don and Volga rivers were also relatively close by. The water-routes connected her to Italy, Constantinople, the Levant, and other important centres of the ancient world.

Trade flourished in the region and helped strengthen the once crumbling economy of Caffa. She even housed over 80,000 people at the time.

Meanwhile, in the vast plains of Mongolia, the death of Kublai Khan in 1294 broke up one of the most massive empires in human history into relatively small shards of land. They were known as the "Khanates," but they weren’t exactly weak. They had strong artillery and an amazing economy. Of these Khanates, the Khanate of the Golden Horde had authority all over Crimea.

The Army had a portion of it filled in with the Tartars. They were an ancient Mongolian nomadic tribe who were defeated by Genghis Khan. By the mid-14th century, the Golden Horde grew dependent on the Tartars to help them govern their vast lands.

There was an influence of Caffa and the Genoese on the region as well, but by the 1340s: political, economic and religious issues started piling up between the Mongols and the Genoese. The communities were no different than a bundle of dynamite. One single spark was all it took for it to explode and create horrendous destruction on a large scale.

Conflicts:

Way up, to the north of Caffa, was situated Tana, a city renowned for being the place one would go to if they wished to get into China. A simple conflict between an Italian trader and a Mongol host was all that was needed. There was bloodshed, and a person was even killed over the course of the event. The local Mongol king arrived on the scene with an army of Tartars. There were fights, big disputes, hostility among the people, and overall, massive bloodshed in the year of 1343, which completely destroyed the city of Tana.

A great war broke out between the Mongols and the Genoese. Massive impenetrable walls were built across Caffa's borders to protect the population from the rival. A massive siege took place. The Tartars assembled at the battle grounds ready for war with heavy armour and strong shields.

They brought with them an amazing artillery, but they were in for a surprise from the little guest that lay beneath their hooves.

But do these political tensions have anything to do with the spread of the plague?

With political frictions such as the war between the Mongols and the Genoese, it helped double the spread of the Black Death worldwide.

"No human activity has been more closely associated with the plague than war."

- John Kelly [ Author of "The Great Mortality"]

The beginning of the spread:

At this point, rumours about a lethal disease spread across the kingdoms like wildfire, but most claimed them to be preposterous tales. As the cases grew further, the plague spread all over India and China. The Black Death now made its way to a new prey in the west, the Mongols.

Over a short course of time, people started dropping dead everywhere. Their corpses were swollen and a terrible stench enveloped the streets. Decaying bodies lay piled up in the corners, and flies were all over the place. The Mongol king grew frustrated with the situation they were in as the Genoese celebrated behind their walls.

The Mongol ruler developed a strategy to defeat his rival and took his people's situation as an opportunity for that. He ordered the army to tie the swollen corpses to a catapult and fling them in the air toward their rival encampments situated behind a wall.

The corpses, with their organs filled with gases from the plague, were more like human balloons. When flung into the air with sufficient velocity, most of them exploded on the soldiers, spraying them with the disease they stored inside. The rodents that lived near the piles of the dead followed the trail of the stench into the city of Caffa. The once-celebrating Genoese, who scoffed at the Mongols, had now become prey to the plague too.

The Black Death may have been lethal, but what helped it expand its domain?

The major infection carriers, rats and fleas, were well suited for the job. The Black Rat [Rattus rattus] was a major infection carrier. Though it was relatively small compared to a brown rat, its adaptability made up for its flaws. The rat could survive a fall from a 5-storey building and could bite down on adobe, lead, and unhardened concrete. It could climb nearly vertical walls and could reproduce a population of 3 million rats over the course of three years.

This rodent has its roots in Asia and is said to have evolved 15,000 years ago. The black rat’s presence is hard to detect since it always sets up an escape route before scavenging for scraps of food in a new area. What made this rodent particularly lethal was that it served as the perfect reservoir for the flea: Xenopsylla Cheopis, or "The Rat Flea."

This flea loves feeding on rodent blood, but it can survive an entire month without a host. It is extremely adaptive to new environments and can live off nearly any surface, be it cloth, baggage, or even swollen corpses. The hind legs of the flea help it take a leap of half a meter, making it the perfect weapon for an infection spread.

Normal fleas have the ingested host blood flow directly into their stomachs, but the plague-infected fleas have a different mechanism. The bacterium blocks the foregut of the flea, preventing the blood from reaching its stomach. The flea is then forced to take more bites from its host in order to survive. The bacterium will continue to multiply in the fleas’ bodies and then be pumped into the bodies of the fleas’ hosts.

Once inside, the bacterium works its way through organs and the lymphatic system, a key defence mechanism in humans, and renders it useless. Once the body’s defence mechanisms are destroyed, it starts killing the host from the inside.

The Consequences:

Corpses lay all over the streets, swollen and decaying. A terrible stench enveloped the city, and rodents laid their nests beside the piles. Feral animals fed on the bodies, and old women and men dragged their loved ones around the streets, looking for help. The infected were locked in their homes and left to die. Family members wouldn’t step out of their houses for the burial of their departed ones. Drunk soldiers looted the dead, searching for anything valuable.

"They sickened by the thousands daily, and died unattended and without help. Many died in the open street, others dying in their houses made it known by the stench of their rotting bodies."

-- Boccaccio, Giovanni

The once peaceful Caffa was now transformed into a catastrophic epidemic. Some survivors locked themselves away from the outside world and stayed hidden in their homes, while others preferred to leave the city. Thousands rushed to the docks, filling in the 200 ships of Caffa. Soldiers wielded swords, attempting to keep the extra population away from the boats since everyone couldn’t fit in. The ship's crew got to work, and they sailed away in the roaring waters, away from their homeland.

Caffa was completely destroyed. The buildings were on fire, and the smoke had spread all across the sky as the remaining survivors made their way to safer lands. Little did they know what lay in the ship’s lower parts: an army of infected rodents, enjoying the company of the new visitors.

The beginning of a global pandemic:

In the summer of 1347, the people of Caffa set their feet on the land of Constantinople, hoping for a new beginning. Days after their arrival, the population began dropping dead. Cases piled up every day, and the situation worsened once again. The plague nearly wiped out 50-70% of the population as it fed on the bodies of its hosts.

Other ships sailed their way all across to the city of Bosporus, where the plague took new routes of expansion. In the west, it spread through Bulgaria, Greece, and Romania and then upwards towards Poland, and in the east, it spread to Asia Minor and then headed over to Persia.

The ships of Caffa didn't stop here. They sailed all the way to the ports of Cyprus, Egypt, Levant, and Sicily.

On arriving at the Venetian land, strict measures had been set up for the people of Caffa. The army was ordered to "torch" any incoming ship that showed signs of the Black Death. The city was kept in a lockdown and the foreigners were kept in quarantine. Matter of fact, the word "quarantine" is derived from a Latin word which means "40 days", referring to the 40-day isolation period the people had to go through.

Though the strategy worked for a while, the plague, with an average infection rate of 2.5 miles a day, managed to wipe out 120,000 Venetian citizens out of the mortal world during the month of January in 1348.

These were hard times for the people alive in the decade. With no sign of a cure, all the people could do was wait for their terrible end.

The Black Death had mercy on none