Befriend a Distant Enemy to Attack One Nearby
It is known that nations that border each other become enemies while nations separated by distance and obstacles make better allies. When you are the strongest in one field, your greatest threat is from the second strongest in your field, not the strongest from another field.
Han Dynasty China
In 110 AD the province of Hunan had suffered through droughts and floods, the harvests were poor and the people starving. The corrupt government only made matters worse and soon the whole province was in chaos. The numerous bands of bandits and robbers that roamed the countryside pillaging and terrorizing the population thwarted any hope of bringing in outside relief. A provincial official by the name of Yu-Hu was appointed full powers to try to restore some order to the province. When he arrived at the district capital he issued a notice that he was going to organized a military force and that he was looking for recruits. First he promised a pardon for past crimes and immunity for anyone who joined up. Then he announced that he was looking for men for three classes of troops. The first class of troops were to consist of men who had committed robbery and murder. They would be the commanders and receive the highest salaries. The second class would consist of men who had committed mere thievery. They would receive the next highest salaries. The third class would consist of men who had joined the robber bands simply because they were lazy and wished to avoid real labor. They would be paid the lowest salaries. Within a couple of weeks Yu-Hu had over three hundred new recruits. When they had been issued uniforms and weapons he had them paraded before him and addressed them as follows: "Your past deeds are now forgiven and you are free from prosecution. But you must still atone for the crimes you have committed against society. To do this you must now go out and hunt down all your past colleagues who have not answered my call." This they did and within a year the fraternity of bandits was extinct and the countryside made safe.