What was the purpose of military operations and job fairs held by various countries during the Spring and Autumn Period? What was the essence of this approach? What was the result?

The main purpose is to occupy. To be more specific, it means the occupation of land and countries. The several overlords that emerged during the Spring and Autumn Period and later the Warring States Period all had the goal of occupying countries and becoming the overlord themselves. At that time, the power of various countries was very objective, and the hegemons that finally emerged all developed from such mutual encroachment. I don’t know what the job fair you are talking about specifically refers to. At that time, all countries were recruiting talents hidden in various places. The main purpose was of course to develop national strength. The essence is to develop national strength and have a certain influence in the war with other countries. Whether it is economics or politics, it requires talents. This was reflected in subsequent historical developments, such as Shang Yang's Reform and so on. As a result, several overlords emerged in the early and late Spring and Autumn Period, such as the earliest Duke Heng of Qi. (If you don’t understand clearly, you can ask. I studied history in high school, haha)