More than two years after South Sudan’s civil war began, its opposition leader landed in the capital, Juba, on Tuesday for a ceremony to restore him as vice president, a step in a peace deal plagued by delay and mistrust.

South Sudan, the world’s youngest nation, was born in 2011 to great international fanfare. But shortly after secession, it spiraled into a civil war that killed thousands and displaced more than two million people.

Nearly two years of peace negotiations in Ethiopia’s capital, Addis Ababa, yielded several cease-fires, and recommitments to cease-fires, that were broken almost immediately.

Now the return of the opposition leader, Riek Machar, puts him basically back where he had started, as the official No. 2 to his chief rival, President Salva Kiir.

The war broke out in 2013 after Machar said he would contend for the leadership of South Sudan’s governing party, the Sudan People’s Liberation Movement.

He was dismissed by Kiir, and fighting erupted in Juba in December 2013, quickly splitting the nation along ethnic lines. Kiir belongs to the Dinka ethnic group, the country’s largest, while Machar is a Nuer.

Opposition leaders say that Dinka soldiers targeted and killed hundreds of Nuer soldiers and civilians in a few days. Clashes then spread across the country as troops vied for control of South Sudan’s oil fields and regional capitals.

Fighters on both sides have been accused of human rights violations, including rape, the wanton killing of civilians and the recruitment of child soldiers. The clashes were further complicated by smaller-scale divisions among the country’s ethnic groups, leaving no clear battle lines in the conflict.

In accordance with the negotiations, the opposition leader, Machar, who had been living in exile at eastern bases in South Sudan and in neighboring Ethiopia, had refused to return without the presence of 1,370 opposition soldiers in Juba, and the last of them arrived last week.