This chapter tracks how the measures on enemy aliens consolidated, evolved and transformed and how the number of enemy aliens grew and changed between 1915 and the beginning of 1917. In this period, policies against enemy aliens became more detailed and regulated new aspects of the enemy aliens’ lives. The chapter follows the processes of convergence and divergence among countries at war. It also deals with the policies adopted and implemented by countries such as Italy, Bulgaria, Romania and Portugal and its colonies that entered the war at a later stage. It also pays attention to the process that transformed enemy aliens into friendly aliens and vice versa. As the war ground on, while anti-alien feelings among the belligerent populations assumed an anti-Semitic and racial character, the warring governments put in place a two-way process that turned some enemy aliens into friendly aliens and citizens and subjects who belonged to specific national or religious minorities into aliens. This double process mainly concerned, directly and indirectly, the multi-ethnic empires at different stages of the war, and varied greatly from government to government.