I've been looking into this topic and I've found many different opinions on the subject. Steven Pinker, in his book 'The Better Angels of Our Nature,' claims that increases in education and accessibility to pacifist literature have directly contributed to violence being less acceptable in modern day society. Pinker also uses the example of decreasing fatalities caused by war over the past century to claim that wars are getting less violent. On the other hand, Tanisha Fazal, in her article 'Dead Wrong?: Battle Deaths, Military Medicine, and Exaggerated Reports of War's Demise, brings up the point that war deaths are not an accurate measure of decreasing violence in war. She uses the example of more advanced military medicine and claims that it softens the death rate in modern warfare. I also remember reading somewhere that the most common way to die in (sussex?) sometime in the 15th century was by murder, is this true?
Source: reddit post