Scenes of elation marked the reopening of the border between Ethiopia and Eritrea on Sept. 11. According to reports, the roads at the Debay Sima-Burre checkpoint, near Eritrea's Assab port, and at the Serha-Zalambessa checkpoint now allow the flow of civilian traffic from one side of the border to the other for the first time in more than 20 years. The move is the latest step in Ethiopian Prime Minister Abiy Ahmed's efforts, alongside his Eritrean counterpart, Isaias Afwerki, to normalize relations between their countries....