New Delhi, Dec. 10 -- Ethiopia 's prime minister loves big projects. With a mega-dam completed on the Nile, Abiy Ahmed now plans Africa's largest airport and a nuclear power plant. But the threat of war is back as the landlocked nation seeks its most audacious feat yet: access to the sea.

The prime minister hailed the country's transformation in a parliamentary address in late October. The capital, Addis Ababa, has seen a development boom. The Grand Ethiopian Renaissance Dam was inaugurated in July. Abiy has called it a "harbinger of tomorrow's dawn" that will end the reliance on foreign aid for Africa's second most populous nation. The country has been one of the world's biggest aid recipients.

But multiple challenges lie ahead that co...