Recent years have seen growing concern over the use of cyber attacks in wartime, but little evidence that these new tools of coercion can change battlefield events. We present the first quantitative analysis of the relationship between cyber activities and physical violence during war. Using new event data from the armed conflict in Ukraine — and additional data from Syria’s civil war — we analyze the dynamics of cyber attacks, and find that such activities have had little or no impact on fighting. In Ukraine — one of the first armed conflicts where both sides deployed such tools extensively — cyber activities failed to compel discernible changes in battlefield behavior. Indeed, hackers on both sides have had difficulty responding to battlefield events, much less shaping them. An analysis of conflict dynamics in Syria produces similar results: the timing of cyber actions is independent of fighting on the ground. Our finding — that cyber attacks are not (yet) effective as tools of coercion in war — has potentially significant implications for other armed conflicts with a digital front.