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A little over three years ago, Ethiopia’s government and the leadership of the northern Tigray region agreed to end a civil war that killed hundreds of thousands of people and displaced millions more.

Missing from that pact, though, was Eritrea — the secretive, militarized nation to the east that fought for decades over independence from Ethiopia before siding with new President Abiy Ahmed against the Tigrayans.

The tables have turned again.

This time Eritrea is on the same side as Tigray following months of rising tensions with Addis Ababa. The governments are deploying troops and military equipment to their border, according to regional diplomats.

The animosity is historical, but has been fueled of late by rhetoric from Abiy over his nation’s lack of access to the ocean — lost through Eritrea’s secession three decades ago.

“Due to our enemies’ plot, keeping Ethiopia a geographic prisoner for so long is not right,” Abiy said at a joint briefing with visiting Turkish President Recep Tayyip Erdoğan this week. “Logistics is the major bottleneck to our growth, and sea access is the key.”

Many suspect Abiy now has eyes on taking Eritrea back.

It’s a region already crippled by fighting. Tigray is still struggling to rebuild, while in neighboring Sudan, a three-year conflict between the army and a paramilitary force has exacted what the United Nations terms the world’s worst humanitarian crisis. To the south, jihadists have been waging war against the Somali government for years.

A broader power play raises the risk of wider conflict.

The United Arab Emirates has backed Abiy with financial aid in recent years, while Egypt and Saudi Arabia positioned themselves as close allies of Eritrea and the Tigrayans. Sudan and Egypt are already angered by Ethiopia’s giant new dam that blocks the flow of the Nile.

Once again, the Horn or Africa sits on a powder keg.