History of Kenshi puts the founding of United Cities and Traders Guild between 100 ~ 1000 years ago, sometime after Shek Kingdom was founded, and is rumored to come from the ashes of a former empire such as the Second Empire.
The United Cities and the Traders Guild seized power and began to institute new laws regarding slavery, where people would be free of the tyranny of the former empire, and only the criminals would be relegated forcefully to the mines and farms. However, much like the Second Empire in the past, the term of 'criminal' was found to be more and more loosely applied.
A few decades ago, the southern plains suffered a significant drought, which in turn caused a severe famine that nearly brought the United Cities to its collective knees. Due to the famine, the southern cities were forced to rely on the Traders' Guild to bring them the supplies they needed to survive. Unfortunately, Shek raiders and other bandits blockaded the routes and took these supplies for themselves. What little did get through was instantly set upon by the nobles in a bidding war, and the lower classes were driven to starvation and rebellion. The resultant fighting claimed many lives, including many nobles and even Emperor Anzai himself, but the rebels were eventually put down and survivors enslaved. This marked the selection of a new Emperor from the Noble's Circle, Emperor Tengu, a cruel and impulsive man known for his lack of common sense. The Red Rebellion had also made much of the farming life unsustainable inside United Cities[11][12].
Sometime after Tengu was chosen, simmering tensions between The Holy Nation and United Cities have broken out into open conflict in recent years, Bast, once a prosperous and fertile area, filled with many farmlands and towns for trading, was razed to the ground in a border conflict with The Holy Nation. The land has since been a warzone where both the Holy Nation and United cities vie endlessly in a stalemate for at least 15 years, trampling underfoot any life that may have once thrived here (with the neighboring border used as a relatively low-intensity buffer zone).