The U.S. backed the country in its independence struggle. Now, it is needed again.
A U.S. intelligence agent is assisting with the prosecution of suspects accused of killing a South Sudanese aid worker and raping his foreign colleagues.
Soldiers killed 114 civilians, raped countless women and attacked funerals in a recent offensive, according to a U.N. report.
Almost half the population face food shortages and 100,000 people are at risk of immediate starvation in South Sudan.
The rest of the 4,000-strong contingent is expected in the country later this year.
At least 82 aid workers have been killed since 2013 in South Sudan, the U.N. says.
Residents of the town reported that militias aligned with the government "went from house to house" looking for people from the Lou and Fertit ethnic groups.
Some 16 million people in the region are in urgent need of food, water and healthcare.
Conflict, poverty and hunger continue to blight the world's youngest country.
A 360 degree video shows how the two-year civil war has left 2.8 million people hungry.