Forces in Ethiopia’s Tigray region said troops from neighbouring Eritrea started a full-scale offensive on Tuesday while heavy fighting was taking place in several areas along the border. Two aid workers confirmed this and reported shelling into a displaced persons’ camp on the outskirts of the village of Ziban Gedena.

The U.S. special envoy for the Horn of Africa, Mike Hammer, said on Tuesday that the United States was aware of Eritrean troops crossing into Ethiopia’s Tigray region and condemned it. Getachew Reda, a spokesman for the Tigray People’s Liberation Front (TPLF), said on Twitter that Eritrea is deploying both its entire army and reservists. Getachew added that Ethiopian troops and special forces from the Amhara region to the south had also joined the offensive.

Earlier in the month, several airstrikes hit Mekele, the Tigrayan capital as fighting resumed between Tigray forces and Ethiopia’s government in late August, shattering a period of relative calm since late March. The director of the city’s flagship Ayder Referral Hospital said two airstrikes on 14 September killed 10 people. The target in Mekele “was a residential neighbourhood,” Kibrom Gebreselassie told The Associated Press.

Before the latest escalation, the relative calm had allowed more humanitarian aid to reach Tigray but those deliveries have now been halted, according to the United Nations. Deliveries to conflict-affected parts of the neighbouring Amhara region have also stopped with thousands reported killed and millions displaced in the Tigray, Amhara and Afar regions since the conflict broke out in November 2020.

It is worth remembering that a major reason why the war has remained protracted is the complication augured by the Eritrean involvement. Mr Abiy’s peace deal with Isaias Afwerki not only ended decades of frost between Addis Ababa and Asmara, but also earned him a Nobel Peace Prize. However, that deal formed the basis for an anti-Tigray front when war broke out in November 2020 which saw Eritrea (whose common border on the Ethiopian side is Tigrayan territory) join forces with Abiy.

For Addis Ababa, the motivation was to ensure that the TPLF stayed in its place; for Asmara, it saw an opportunity to exact revenge for the border wars it fought with Ethiopia during the 17 years it was in power at the centre. Eritrean forces pulled out of Tigray in 2021 following a series of denials amid the threat and applications of international sanctions. The cause of its re-entry into the fray is not clear, but it has definitely complicated two efforts at peacebuilding: one led by the African Union with former Nigerian President Olusegun Obasanjo as lead mediator and a US-Kenya peace effort.

This escalation comes at a time when Tigray has signalled its readiness to negotiate with Addis Ababa to end the conflict following violations of previous ceasefires. The latest developments could simply be the opportunistic calculation by the anti-Tigray coalition that has smelled blood and is moving in for the kill. This has the potential to, not only prolong the conflict but also destabilise the wider region, especially in Eritrea where a mass mobilisation, announced a week ago, is underway. Already, forced conscription into the Eritrean military has been the driving factor for young Eritreans making the dangerous effort to illegally migrate to Europe for some time now.

Meanwhile, the war in Tigray has exacerbated a catastrophic humanitarian crisis that might see six million people in the Horn of Africa region suffer from food insecurity. It is no accident that some of the first shipments of Ukrainian grain since the start of the conflict in Eastern Europe have been destined for Ethiopia. The government called on reservists to report to their respective head offices, while advising that they carry their own supplies, including blankets and water containers. This raises the prospects of even more rights abuses, especially for a military that cannot sufficiently provide for its forces. Optimism is dwindling and time is running out for resolving one of Africa’s worst conflicts in recent memory.