Northern and central China was often a theater of imperial dynastic conflict which resulted in waves of Han Chinese refugees fleeing to the south. With dynastic changes, wars, and foreign invasions, Han Chinese living in central China were forced to expand into the unfamiliar and southern regions in large numbers. As the number of Han Chinese immigrants into the Yue coastal regions increased, many Chinese families joined them to escape political unrest, military service, tax obligations, persecution, or sought new opportunities. As early arrivals took advantage of the easily accessible fertile land, latecomers had to continue migrating to more remote areas. Conflicts would sometimes arise between the two groups but eventually Han Chinese immigrants from the northern plains moved south to form ad hoc groups and take on the role as powerful local political leaders, many of whom accepted Chinese government titles. Each new wave of Han immigrants exerted additional pressure on the indigenous Yue inhabitants as the Han Chinese in southern China gradually became the predominant ethnic group in local life while displacing the Yue tribes into more mountainous and remote border areas.