Who is fighting who? * The Ethiopian National Defence Force: It has up to 50,000 fighters in Tigray, with Russian T-55 and T-72 tanks. It has massive air superiority from Russian fighter jets, helicopter gunships, and missile systems. However, while the powerful Northern Command is notionally loyal, it is based in Tigray and its assets are under rebel control. * Tigray People’s Liberation Front: The TPLF has about 250,000 soldiers, but fewer than 60,000 effective fighters. However, it has a formidable history. Tigrayans drove out the Marxist Derg regime in 1991 and bore the brunt of the Eritrean war. Who could be dragged in? * Eritrea: President Isaias Afwerki detests the TPLF and controls a 200,000-strong army. There are credible reports that Eritrean troops have already crossed the border. * Sudan: There is a long-running dispute between Sudan and Ethiopia over the fertile Fashqa triangle, and a new one over Ethiopia’s $4 billion dam on the Blue Nile, which Egypt and Sudan say threatens their water supplies. * Egypt: Sudan and Egypt are holding military exercises scheduled before the Tigray conflict began but intended as a joint show of force amid the dispute over the dam. * Somalia: Ethiopia shares a long and porous border with Somalia, and Ethiopian troops are in Somalia with an African Union peacekeeping force. * Djibouti: It borders Eritrea, Ethiopia and Somalia, and its port is Ethiopia’s only access to the sea.