The Russia-Ukraine war demonstrates the crucial role of technology in modern warfare. The use of digital networks, information infrastructure, space technology, and artificial intelligence has distinct military advantages, but raises challenges as well. This essay focuses on the way it exacerbates a rather familiar challenge: the “civilianization of warfare.” Today's high-technology warfare lowers the threshold for civilian participation in the war effort. A notable example is the widespread use of smartphone apps by Ukrainian civilians, who thereby help the armed forces defend against Russian aggression. Through the lenses of international humanitarian law, conventional just war theory, and revisionist just war theory, this essay evaluates the normative dimensions of such civilian participation. The analysis shows that civilians can lose their legal protections when they use these apps to directly participate in hostilities, and this loss of immunity can be justified by Michael Walzer's conventional just war theory. Revisionism, however, puts the justness of the war at the forefront, and so sheds doubt on the moral liability of Ukrainian civilians. Considering the broader implications, including the blurring combatant-civilian distinction, indicates that such civilianization of warfare should not be welcomed; the risks will often outweigh the benefits. At a minimum, states ought to exercise restraint in mobilizing civilians and inform them of the implications of their actions.