The Niger Delta Avengers are back. After nearly five months of silence, the militant group has released a bellicose statement promising new attacks. It previously gained acclaim by conducting a few high-profile attacks on Nigeria's oil and natural gas infrastructure, disrupting the production of hundreds of thousands of barrels per day and stoking the ire of the Nigerian federal government during the 2016 campaign. On Nov. 3, the Niger Delta Avengers declared they would resume their attacks on the region's energy infrastructure, bringing an end to its moratorium on such attacks....