As the Song dynasty was established in Beijing in 900AD, a large attack force began to approach Wuzhou. Zhu Wen was unable to send his troops back down to southern China in time to intercept, so the governor of Wuzhou had no choice but to broker a peace with the Khmer leadership. Although the kingdom agreed to pay small amounts of tribute, it was far from what the imperialist general Wen wished for, and even as the peace began, he began preparing armies for a second assault.
However, any hope of peace was shattered when, in what the emperor considered an intolerable display of disloyalty, the Khmer kingdom signed an agreement with Japan, agreeing to pay them vast amounts of tribute in return for total protection and integration into what was now known as the Empire of Japan. The Khmer even began using the Chinese name for the area, Annam, to add insult to injury. Enraged, the Song Emperor yelled that he had been "trolled", and ordered that every Khmer city be raised to the ground, no matter what the cost.
Historians agree that by 1000AD, China's population numbered in the millions, and this allowed the Song military to grow to sizes never before possible.
Additionally, new technological advances allowed the Song to manufacture great siege engines, and apparently allowed for pointier spears for Chinese spearmen somehow.
The Tibetan Empire was significantly smaller and militarily weaker than the Song. Due to the magical rainbow marshmallow fairy powers of the great wall, the Tibetan army hadn't been able to launch any raids on Western China for centuries, and in 1027AD the struggling kingdom gave up its independence and formally came under the Song's protection. However, Emperor Shenzong of Song was not satisfied, and still desired expansion into the Jiaozhi region.
To achieve this, Shenzong ordered general Yue Fei to make landfall just outside of the Khmer capital of Bang Makok with an army far larger than that which had invaded the same kingdom in the Tang era. Legend has it, there were so many siege units involved in the strike, some of them accidentally bombarded the coastal village of Panduranga instead of the capital by accident, even though it was hundreds of miles away.
In early 1047AD the Song forces finally breached the walls of Bangkok and promptly set fire to much of the city proper, establishing the military base Mangu to allow troops to regroup before pushing on to the city of Panduranga, the last Khmer outpost in Jiaozhi.
Meanwhile, the Japanese responded to this act of Chinese aggression by launching a meager attack force onto the Korean peninsula. However, the Japanese troops were no match for the elite Song Cho-Ko-Nus, and were quickly repelled back to Manchuria, but not before accidentally killing one of Shenzong's favorite pet deer in the process.
To avenge the death of his beloved deer, Shenzong ordered all remaining Khmer cities to be destroyed. On his orders, Chinese troops sacked Panduranga and burned the city to the ground.
Meanwhile, the Khmer government, which at this point had fled to the one remaining Khmer city of Pagan, heard the news of the destruction of their last city in Jiaozhi. The Khmer king reportedly started shouting at his advisors upon hearing about Panduranga's destruction, demanding to know "HOW'D IT GET BURNED"!?
Tragically, the king never got an answer, as Song forces knocked on his door before anyone could answer. Dutifully following orders, the Song military burned the city to the ground, and trapped the remaining Khmer officials (who had not fled to Japan) in a giant wicker man, setting it on fire and roasting them alive. Having heard of the utter destruction of their province of Annam, the Japanese government demanded that the Song pay them damages for all of the lives lost as a result of Chinese aggression in the region, which evidently amounted to about 50 gold pieces. After this payment was received, the Japanese government began negotiations for peace with the Song leadership.
In 1084, Confucian Scholars in the Song government informed the emperor that having a source of gold would allow Chinese workers to build the Shwedagon Paya twice as fast. The emperor had no idea what the Shwedagon Paya was, or why he would want to build it, or even how gold would magically halve the amount of time it took to build it. Nevertheless, he trusted his advisors, and forcibly relocated part of Wuzhou's population to the settlement of Mandelei later that year.
By the 12th Century AD, Song traders had contacted several new imperial forces in the west, and had begun trading with them. Islam, a religion that had originated in the Arabian peninsula, had spread like wildfire through Europe, and these great Muslim European Caliphates were initially wary of the Taoist Traders.
However, a new nation to the north was significantly less friendly to the Song. The barbarians to the north, which had been trapped outside the Great Wall for hundreds of years, finally united under the great military commander Genghis Khan. As a result, the Great Wall's magical sugarplum fairy powers would no longer work on them. In what is considered the most ironic declaration of war ever, this new Mongol nation declared war on China in 1189AD, bringing an end to nearly 100 years of peace for the Song Dynasty.