The armed clashes along the border between Sudan and Ethiopia are the latest twist in a decades-old history of rivalry between the two countries, though it is rare for the two armies to fight one another directly over territory.
The immediate issue is a disputed area known as al-Fashaga, where the north-west of Ethiopia’s Amhara region meets Sudan’s breadbasket Gedaref state.
Although the approximate border between the two countries is well-known – travelers like to say that Ethiopia starts when the Sudanese plains give way to the first mountains – the exact boundary is rarely demarcated on the ground.
Borders in the Horn of Africa are fiercely disputed. Ethiopia fought a war with Somalia in 1977 over the disputed region of the Ogaden.
In 1998 it fought Eritrea over a small piece of contested land called Badme.
About 80,000 soldiers died in that war which led to deep bitterness between the countries, especially as Ethiopia refused to withdraw from Badme town even though the International Court of Justice awarded most of the territory to Eritrea.
It was reoccupied by Eritrean troops during the fighting in Tigray in November 2020.
After the 1998 war, Ethiopia and Sudan revived long-dormant talks to settle the exact location of their 744km-long (462 miles) boundary.
The most difficult area to resolve was Fashaga. According to the colonial-era treaties of 1902 and 1907, the international boundary runs to the east.
This means that the land belongs to Sudan – but Ethiopians had settled in the area and were cultivating there and paying their taxes to Ethiopian authorities.