At the western gate of the biggest United Nations base in South Sudan, hundreds of people carrying bundles of possessions push and jostle. Peacekeeping soldiers wearing blue helmets hold them back, forcing them into a queue of sorts.Beyond the entrance lies one of the most fetid and overcrowded patches of land on earth: a UN compound transformed into a makeshift refugee camp with 17,000 people. Those at the gate are not struggling to get out; they are doing their utmost to get in and make their home amid the filth and squalor. Their willingness to endure this hardship as the price of safety is a measure of the desperation caused by South Sudan’s civil war.The people crowding to live within the perimeter walls of the main UN camp here in Juba, the capital, are from the Nuer tribe of