section_path: History
section_name: History
paragraph_text: History
  
  The earliest evidence of prehistoric warfare is a Mesolithic cemetery in Jebel Sahaba, which has been determined to be about 13,400 years old. About forty-five percent of the skeletons there displayed signs of violent death, specifically traumatic bone lesions.
  
  In War Before Civilization, Lawrence H. Keeley, a professor at the University of Illinois, says approximately 90–95% of known societies throughout history engaged in at least occasional warfare, and many fought constantly. Keeley describes several styles of primitive combat such as small raids, large raids, and massacres. All of these forms of warfare were used by primitive societies, a finding supported by other researchers. Keeley explains that early war raids were not well organized, as the participants did not have any formal training. Scarcity of resources meant defensive works were not a cost-effective way to protect the society against enemy raids.
  
  William Rubinstein wrote "Pre-literate societies, even those organized in a relatively advanced way, were renowned for their studied cruelty.'" Since the rise of the state some 5,000 years ago, military activity has continued over much of the globe. The invention of gunpowder, and its eventual use in warfare, together with the acceleration of technological advances have fomented major changes to war itself.
  
  In Western Europe, since the late 18th century, more than 150 conflicts and about 600 battles have taken place. During the 20th century, war resulted in a dramatic intensification of the pace of social changes, and was a crucial catalyst for the growth of left-wing politics.
  
  Mao Zedong urged the socialist camp not to fear nuclear war with the United States since, even if "half of mankind died, the other half would remain while imperialism would be razed to the ground and the whole world would become socialist."
  
  A distinctive feature of war since 1945 is that combat has largely been a matter of civil wars and insurgencies. The major exceptions were the Korean War, the Indo-Pakistani War of 1971, the Iran–Iraq War, the Gulf War, the Eritrean–Ethiopian War, and the Russo-Ukrainian War.
  
  The Human Security Report 2005 documented a significant decline in the number and severity of armed conflicts since the end of the Cold War in the early 1990s. However, the evidence examined in the 2008 edition of the Center for International Development and Conflict Management's "Peace and Conflict" study indicated the overall decline in conflicts had stalled.