When Kenyan police arrived in Haiti as part of a U.N.-backed mission earlier this year to quell gang violence, hopes were high.

Gang violence surged in Haiti, with a paroxysm of bloodshed leaving at least 150 dead and driving the charity Doctors Without Borders to suspend its operations in the country. Haiti has been racked by armed groups who operate with impunity, unrestrained by a government that controls little of the nation’s actual territory.