The Yellow River is the second-longest river in China, second only to the Yangtze River (长江). The Yellow River has often been referred to as “China’s Sorrow,” a metaphor for all the devastating floods and disasters that stemmed from it. Historical documents and government records indicate that the Yellow River has overflown over 1,000 times over the past 2,000 years.

The low-lying city of Kaifeng sat in the epicentre of the floods. Over the past 3,000 years, it has seen around 40 major floods. Beneath its surface, there is a 20-meter-thick archaeological sequence — dating from the Bronze age to the present — that powerfully documents the devastation of this, at one time, the largest city in the world; 3-metre of these belongs to the 1642 flood.

According to the article Geoarchaeological Evidence of the AD 1642 Yellow River Flood that Destroyed Kaifeng by Nature, the elevation of the Yellow River was higher than that of Kaifeng and that near Kaifeng, which was located less than ten kilometres south of the River, the average depth of the River was around 35 meters.

By the middle of the 15th century, the Ming Dynasty's had established a robust flood-control system that had prevented flood disasters for over a century. Furthermore, like many other cities in Central China, Kaifeng had long had the tradition of building a thick and solid city wall to protect itself from invaders and floods.

However, none of these protective measures worked in 1642 when Kaifeng saw, arguably, one of the worst floods in its recorded history. The damage was not inevitable — it was man-made.

On 14th February 1642, Li Zi-cheng carried out his third attempt to take down the city of Kaifeng. However, unlike the previous two times where he suffered heavy losses, he decided to besiege rather than attack.

His troops surrounded the city walls. Hundreds of thousands of soldiers and civilians were trapped inside; food and supplies became so scarce that it was reported, some people, out of desperation, turned to cannibalism.

This strategy was successful. Inside the city was full of dying hungry people; action had to be taken. Governor Henan, Gao Mingheng, believed if the situation continued, death and hunger would lead people to open the city gate and let Li and his bandits into the city. Since Kaifeng is protected by a thick and high city wall, he envisaged breaking the dike, having the water flow around the city and thus drown off the rebels stationed outside the city.

In his book, The Jews of Kaifeng, China: History, Culture and Religion, Xu Xin (徐新, 1949–present), Diane and Guilford Glazer Chair Professor of Jewish and Israel Studies at Nanjing University, noted that when it became clear the city could not hold out any longer, "The governor of Kaifeng ordered the waters of the Yellow River unleashed in hopes of destroying the rebel army…. The dikes were broken, but instead of hurting the rebels, the raging waters swept over the low-lying city, drowning a citizenry that was completely unprepared."

An alternate version of the story was that Emperor Chong-zhen (崇祯皇帝, reign 1627–1644) sent in the rescue army; before the troops entered the city, a commander ordered for the destruction of a section of the dike to break the siege. He believed the high-velocity flood would hit the rebels and free up Kaifeng. Rebel leader Li Zi-cheng found out about this beforehand and moved his troops to a higher ground — where the water could not plausibly reach — and ordered his men to break the dike at a different point. He believed that this would catch Kaifeng's defence off guard and leave his troops unscathed because of their geographical position.

In the end, both sides — defender of Kaifeng and attacker of Kaifeng — on 15th September 1642, demolished different parts of the dike at roughly the same time. This resulted in a flood more catastrophic and destructive than either had intended.

According to Roger Des Vorges, “The two resulting streams soon converged in a single rampaging torrent that smashed into the north wall of the Kaifeng.”

The Kaifeng synagogue that was re-constructed in 1279 was utterly wiped out. Most of the congregation's Holy Books were submerged in water. The bits and pieces that were rescued, under the instruction of the community leaders, were assembled into one complete Torah, and this then became the lifeline from which the Jews rebuilt their religious centre.

Out of the roughly 5,000 Jews, more than half were killed. By the time they made it to the northern bank of the Yellow River, fragments of only about 200 families were accounted for. Professor Xu Xin, his book The Jews of Kaifeng, China: History, Culture and Religion, commented on the significant reduction in the size of the community, “The 1489 inscription states that there were seventy clans in the community and names seventeen of them. When the survivors finally returned to their homes after the flood, the number of clans had been reduced to seven: Li, Jin, Shi, Zhao, Gao, Ai and Zhang. All the other clans were gone. When Ai Tian met Ricci, he mentioned that there were ten or twelve clans of Israelites in Kaifeng. Wang Yisha, formerly the curator of the Kaifeng Municipal Museum, believes that some of the clans maybe have been wiped out in the flood, but that others never returned to the city and instead migrated to new homes in other parts of the country. Whatever the reason, the local Jews now had only seven surnames. The community was never the same.”

Kaifeng was also now different. As the overland Silk Road diminished significantly in importance, this inland city grew further away from the economic centre, which had been shifted to the eastern coastal cities.

The major religions in China are individual focused rather than community based. For example, in Buddhism, worshippers mostly did not have relationship with the monasteries — they were free to worship anywhere they wanted; the monks also did not work on building a relationship between the Buddhist God and the individuals or enforced any ritual practices — believers were free to attend, or not, any services they liked. Buddhism, thus, was a religion without a strong institution, or organizational power, which worked well with the ruling regime.

Judaism, like most of the religions in the West, is organised by congregation by which the individual worshipers were attached and committed. The congregation had specific religious leaders, worship compounds, provided services from education to welfare, and had authority in interpreting the law and conducting rituals. The congregational organization provided a cushion for the Jews and reduced the speed of their assimilation into the host society.