Eritrean troops have crossed into Ethiopia's Tigray region, pushing a renewed rebel war toward an open conflict between two countries — terrible news for a corner of Africa already stretched past its limits.

• Eritrean forces are moving south toward Tigray's capital, and Ethiopia has told them to leave immediately.
• The rebel Tigray People's Liberation Front now leads an alliance of seven armed groups, making this fight bigger than the 2020–22 war that killed 600,000 people.
• Eritrea has met with Egypt, Sudan, and Somalia about a joint military response, and relations with Ethiopia have formally collapsed.
• Sudan, South Sudan, Somalia, Chad, and Libya are all close to breaking already, so refugees, weapons, and fighters would flow straight across their borders.
• Rival camps — Israel and the UAE on one side, Turkey, Saudi Arabia, Egypt, and Qatar on the other — are set to pour in money and guns and turn it into a proxy war.

Outlook: A direct clash between Ethiopian and Eritrean forces looks imminent, and the main question now is how far the fighting and the hunger spread beyond Ethiopia.