Papua New Guinea (PNG) received its name from Spanish explorers in the early 1500s. Papua referred to the natives’ frizzy hair and New Guinea extended the name when a later explorer decided the locals resembled the peoples in Africa’s Guinea. The area was extremely diverse, with more than 700 languages spoken by the ethnic groups that inhabited the interior. Traditionally, PNG ethnicities participated in low-level, continual endemic warfare, meaning that the groups’ warrior classes frequently clashed. Pig theft and other petty crimes fueled interethnic disputes. Some tribes even chose to cannibalize their enemies, a process these warriors believed would allow them to take revenge and assume that person’s power.

For more than 300 years, the imperialist nations took little interest in the area. The Spanish and ...