It's extreme economic shocks generally. As in sudden changes in economic conditions that lead to a rapid and pervasive decline in living conditions. It's clearl

It's extreme economic shocks generally. As in sudden changes in economic conditions that lead to a rapid and pervasive decline in living conditions. It's clearly not any absolute level of poverty. The poverty level that will trigger war in Bangladesh is far lower than what would trigger war in the US. And a country at South Sudanese levels of poverty going to a slightly higher level of development (say Bangladeshi levels) wouldn't trigger conflict, even if they were still far worse off than levels that would trigger war in better off countries. But the absolute floor at which war (or widespread systemic violence and civil unrest at least) becomes almost inevitable is when people can no longer afford food. There have been a few studies that suggest a link between sudden increases in food prices and civil unrest and wars.