In September 2018, Abiy Ahmed and Isaias Afwerki crossed from Ethiopia into Eritrea and Eritrea into Ethiopia at border points that had been sealed for twenty years, embraced in front of crowds that had lived their entire adult lives in the shadow of a war neither country had fully processed, and announced that the conflict between their two states was over. The moment was genuine enough to win Abiy a Nobel Peace Prize. It was also, in retrospect, a personal transaction between two leaders rather than a structural transformation between two states — and personal transactions between authoritarian leaders do not outlast the interests that produced them.
In 2026, those interests have diverged sharply. Eritrea has signed defence agreements with Egypt, granted Egyptian forces basing rights on its territory, co-hosted joint military exercises with a country that openly frames Ethiopia as a strategic threat, and maintained a military presence inside Tigray that the Pretoria Agreement nominally required withdrawn. Abiy Ahmed is simultaneously managing active insurgencies in Amhara and Oromia, a collapsing peace deal in Tigray, and the most diplomatically isolated regional position Ethiopia has occupied in decades. The 2018 peace has not simply cooled. It has structurally reversed, and the Horn of Africa is not paying adequate attention to what that reversal means in military terms.
What the 2018 deal actually was — and what it was not
The Algiers Agreement of 2000 had nominally ended the 1998–2000 Ethiopia-Eritrea war, but it left the countries in a condition that analysts characterised as no peace, no war: the border was sealed, diplomatic relations were severed, and a frozen confrontation consumed the defence budgets and political attention of both governments for eighteen years. What Abiy and Isaias negotiated in 2018 was not a formal peace treaty with demarcated borders, verified withdrawals, or institutional mechanisms for dispute resolution. It was a political declaration — a normalisation of relations driven by Abiy's desire for a diplomatic breakthrough and Isaias's calculation that opening to a newly reformist Ethiopian leader was better than continued isolation.
The Eritrea-Ethiopia Boundary Commission had already issued its final and binding delimitation decision in 2002, awarding the contested town of Badme to Eritrea. Ethiopia had refused to implement it for sixteen years. The 2018 deal included Abiy's acceptance of that delimitation, but the physical demarcation of the border — the actual placement of markers in the ground, the definition of where one country ends and the other begins — was never completed. The border remains, in substantial portions, defined only on paper and in dispute on the ground. That undemarcated border is now a military risk in a way it was not when both governments were nominally committed to the 2018 framework.
What the deal did produce, tangibly, was the opening of border crossings, the resumption of flights between Addis Ababa and Asmara, and — most consequentially — the military cooperation that made Eritrean intervention in the Tigray war possible. Isaias used the partnership with Abiy to do what his government had wanted to do since the TPLF consolidated power in Addis Ababa in 1991: break the Tigray People's Liberation Front as a governing force and eliminate the organisation that had humiliated Eritrea in the 1998 war and sustained a hostile posture toward Asmara from its position inside Ethiopia's ruling coalition. The Tigray war was, among other things, Eritrea settling accounts — and it was Eritrea using its partnership with Abiy to do so with Ethiopian military cover.
The divergence of interests after Pretoria
The Pretoria Agreement of November 2022 ended the Tigray war's active phase, and it did so in ways that created structural divergence between Ethiopia's and Eritrea's post-war interests. Ethiopia needed the agreement to stop a war that had imposed severe international pressure, generated documented atrocities that were damaging Abiy's international standing, and consumed military resources that the government needed for its internal conflicts in Amhara and Oromia. Eritrea had no parallel incentive for the agreement and no commitment to its terms. Isaias had not signed Pretoria, was not a party to its implementation architecture, and had achieved his primary objective — the TPLF's removal from federal power — before the agreement was reached.
The requirement that Eritrean forces withdraw from Ethiopian territory was a Pretoria obligation that Eritrea has never fully honoured. Eritrean forces remain present along the Tigray border in areas that are technically Ethiopian sovereign territory, maintaining a presence that gives Asmara leverage over the Tigray situation and a military foothold that the federal government in Addis Ababa has not been able to compel it to relinquish. That presence is not a residual administrative oversight. It is a deliberate positioning that reflects Eritrea's assessment that maintaining physical presence in Tigray is worth the diplomatic cost of non-compliance with an agreement it never signed.
The deeper divergence is strategic. Abiy's external agenda — Red Sea access through Somaliland, regional leadership through IGAD, assertive positioning against Somalia — is precisely the kind of Ethiopian expansionism that Eritrea's entire political identity has been built around resisting. A landlocked Ethiopia seeking maritime access and projecting regional dominance is not an Ethiopia that serves Eritrea's interests. An Ethiopia weakened by internal insurgencies, diplomatically isolated, and unable to project power northward is considerably more attractive from Asmara's perspective. Isaias has every incentive to allow Ethiopia's current difficulties to deepen rather than to stabilise them.
The Egypt factor and what it changes
The formalisation of the Egypt-Eritrea strategic partnership is the single development that most changes the military risk calculation on the Ethiopia-Eritrea border. Egypt has positioned its relationship with Eritrea explicitly as part of its response to Ethiopian ambitions on the Nile — the Grand Ethiopian Renaissance Dam, now generating electricity and filling in ways that Cairo regards as an existential threat to Egyptian water security, has made Ethiopia Egypt's primary strategic adversary in Africa. Egypt has the motivation, the resources, and now the geographic positioning to impose costs on Ethiopia from the north.
Egyptian forces on Eritrean territory represent something qualitatively different from Eritrea operating alone. Eritrea's military, though large relative to its population and battle-hardened through decades of conflict, is constrained by the country's severe economic limitations. Egypt brings resources, advanced weapons systems including drones and artillery, and an intelligence and logistics capacity that Eritrea cannot replicate independently. The joint military exercises conducted in 2025 and 2026 on Eritrean soil were not symbolic. They were capability-building exercises that give Egypt the ability to project military force toward Ethiopia's northern border from Eritrean territory — and that give Eritrea Egyptian military backing if its border confrontation with Ethiopia escalates.
The Somalia dimension adds a third vector. Somalia's formal defence partnership with Egypt, signed in 2024 and expanded in 2025, means that the anti-Ethiopia coalition now has a component on Ethiopia's eastern flank as well as its northern one. Ethiopia is not surrounded in a military sense — the coalition's coherence is political rather than operational, and its members have competing interests with each other as well as shared interests against Ethiopia — but the diplomatic and strategic encirclement is real. Abiy Ahmed is managing his worst internal security environment in a decade while facing the most coordinated external pressure Ethiopia has experienced since the Derg period.
The troop signals and what they indicate
Detailed independent reporting on Eritrean military deployments is nearly impossible given Asmara's information controls, but satellite imagery analysis and cross-border reporting from Tigray indicate increased Eritrean military activity in the border zones since late 2025. Eritrean troop concentrations near the Tigray border have not decreased since Pretoria. In some areas they appear to have consolidated. The specific locations of Eritrean positioning correspond to areas that were contested in the 1998–2000 war and that include both the Badme triangle — which the boundary commission awarded to Eritrea but which remains physically in Ethiopian-administered territory — and mountain passes that have strategic value in any conventional military confrontation.
On the Ethiopian side, the federal military's attention and resources have been directed primarily at the Amhara and Oromia conflicts. The Ethiopian Northern Command, which faces Eritrea, has not been reinforced to levels that would reflect a serious assessment of the Eritrean threat. This disproportion — Eritrea concentrating while Ethiopia deploys elsewhere — is either a deliberate Eritrean probing of Ethiopian vulnerability or a positioning for opportunistic pressure if the Amhara or Tigray situations deteriorate further. Neither interpretation is reassuring.
The most significant troop signal is the continued Eritrean presence inside Tigray proper. Eritrean forces in Tigray serve multiple functions simultaneously: they give Eritrea leverage over the TPLF's political calculations, they maintain a buffer zone between Eritrean territory and a re-armed Tigray, and they represent a military asset that can be used offensively or defensively depending on how the situation evolves. The TPLF's recent vote to reclaim Tigray and repudiate the Pretoria Agreement's transitional governance arrangements creates a direct incentive for Eritrea to maintain and potentially reinforce that presence — the last thing Asmara wants is a newly assertive TPLF controlling Tigray's border with Eritrea without Eritrean forces in place to constrain it.
Why the 2018 war happened and why the conditions for another are accumulating
The 1998 Ethiopia-Eritrea war began over a border dispute in the Badme area that both governments allowed to escalate rather than manage, in a political environment where neither leader could absorb the domestic cost of appearing to concede to the other. The specific trigger — a skirmish between local forces in May 1998 — was the proximate cause of a war whose underlying causes were the unresolved border, the accumulated grievances of the post-independence relationship, and the political dynamics within each government that made escalation easier than de-escalation.
The structural conditions for a similar dynamic are present in 2026. The border remains undemarcated. Both governments face internal pressures that make appearing strong against a historical adversary politically useful. The specific trigger for the 1998 war — a localised incident involving forces with different accounts of where the boundary runs — is entirely possible in areas where Eritrean forces are present on territory that Ethiopia administers. And the Egypt factor introduces a new variable: if Eritrea believes that Egypt will provide military and diplomatic backing in a confrontation with Ethiopia, Isaias's risk tolerance for border escalation increases in ways that it would not if Eritrea were acting alone.
The difference between 1998 and 2026 is that Ethiopia is considerably weaker internally now than it was then. In 1998, the TPLF-led government was politically coherent and militarily capable. In 2026, the Ethiopian federal government is fighting two active insurgencies, managing a collapsed peace deal in Tigray, and operating under the most severe international scrutiny of any period since the 1980s. A miscalculation on the Eritrean border in this environment would not simply produce a bilateral war. It would produce a multi-front crisis that would test the Ethiopian state's coherence in ways that might not be survivable as a unified entity.
What analysts and policymakers are missing
The analytical community working on the Horn has focused heavily on the TPLF's Axum vote, on El Fasher, on the ATMIS drawdown in Somalia — all serious issues demanding attention. The Ethiopia-Eritrea military trajectory has received substantially less analytical bandwidth, partly because Eritrea's information closure makes it hard to report on with confidence, and partly because the 2018 peace deal created an assumption of normalised relations that the facts on the ground have now decisively overtaken.
The assumption that needs to be retired is that the Abiy-Isaias personal relationship constitutes a durable constraint on Ethiopia-Eritrea escalation. That relationship was never institutionalised, never embedded in treaty mechanisms that would function independently of the two leaders' political calculations, and never survived the test of the post-Pretoria period. What replaced it is a situation in which Eritrea has aligned with Ethiopia's primary external adversary, maintains forces on Ethiopian-administered territory, and has a military posture that reflects assessment of Ethiopian weakness rather than commitment to partnership.
The African Union's Peace and Security Council has no established framework for managing Ethiopia-Eritrea escalation. The United States, which played a significant role in the Pretoria process through its special envoy, has reduced its Horn engagement. The EU's attention is directed elsewhere. IGAD, the regional body most logically positioned to play a mediating role, is structurally compromised by the fact that Ethiopia is its dominant member and that Eritrea has historically refused to engage meaningfully with the organisation. The diplomatic infrastructure for managing a crisis between Addis Ababa and Asmara does not exist in a form adequate to the risk that is building.
The Horn of Africa cannot absorb another Ethiopia-Eritrea war. The 1998–2000 conflict killed between 70,000 and 100,000 people, generated mass displacement on both sides, destroyed the infrastructure of normalisation that a generation of effort had built, and contributed directly to the conditions that produced two decades of regional instability. A new conflict in 2026, with Egypt involved from Eritrean territory, with Ethiopia simultaneously managing Amhara and Oromia, and with the Tigray peace deal already collapsing, would be catastrophic on a scale that makes the original war look manageable. The international community's failure to treat this as the urgent priority it is reflects exactly the kind of anticipatory blindness that has made every previous Horn crisis worse than it needed to be.