Abstract: We present new evidence about the relationship between military conflict and city population growth in Europe from the fall of Charlemagne{\^a}€{\texttrademark}s empire to the start of the Industrial Revolution. Military conflict was a main feature of European history. We argue that cities were safe harbors from conflict threats. To test this argument, we construct a novel database that geocodes the locations of 1,091 conflicts and 676 cities between 800 and 1799. We find a significant, positive, and robust relationship that runs from conflict exposure to city population growth. Our analysis suggests that military conflict played a key role in the rise of urban Europe.