To me, it is kind of crazy to me that Ethiopia wouldn't just take a slither of Eritrea to connect them to the coast. They were bigger and could easily have done it when giving Eritreans their independence? I ask this because, with Eritrean independence, Ethiopia became the world's most populous landlocked country.
Just registered for the site, but I do know a bit about this! Following World War 2, Ethiopia wanted Eritrea, and the UN in 1950 came up with an agreement in which they would be a Federation together. By the end of the decade it was clear Ethiopian interest reigned supreme, and Eritrean separatists - predominately Muslim and known as the Eritrean Liberation Front (ELF) - began their armed struggle for Independence in 1961. The "Federation of Ethiopia and Eritrea" was purposely dissolved the following year and Eritrea was simply annexed by Ethiopia immediately.
In 1974, a coup flung Ethiopia in to the Soviet's sphere of influence, and Ethiopia erupted into civil war. The ELF had support from the United States, but by 1977 the ELF became eclipsed by the Eritrean People's Liberation Front (EPLF), who took over the show with their mix of Nationalism and Socialism. That same year, Somalia invaded Ethiopia over a longstanding border dispute, taking advantage of the warring factions within Ethiopia (it didn't work well for them, up until right now infact). The EPLF used all this chaos to their advantage. By the late 80's, the Ethiopian Marxist government had lost the support of the Soviet Union, and the nation was overwhelmed with Eritrean (also Marxist leaning) rebels and Ethiopian anti-government forces. In 1991, the EPLF and Ethiopian rebel groups took Addis Ababa. Jimmy Carter helped host peace talks, and it was agreed that Eritrea would hold a referendum for Independence. Eritrean's voted two years later for independence.
The entire territory that had been Eritrea during Ethiopian rule simply became Eritrea. Ethiopia could not protest, though the two went to war at the end of the decade yet again, and low(er) level fighting continued only until their official peace agreement in July 2018, which was the main reason current Ethiopian Prime Minister Abiy Ahmed was awarded the 2019 Nobel Peace Price recently.
And, for those curious, the EPLF simply became the People's Front for Democracy and Justice (PFJD) in 1991, which advocated for the things in their name along with peasant power and new African Leadership. Zero percent of that came into fruition, and the party remains the only legal one in Eritrea. The party itself hasn't even had a meeting in nearly two decades.