South Sudan's President Salva Kiir (L) and Sudan's President Omar Hassan al-Bashir attend the Independence Day ceremony in South Sudan's capital Juba, July 9, 2011.

South Sudan, August 11, 2010 - Many cattle keepers refused to surrender their weapons during the last disarmament program. According to them, they have to remain armed to defend themselves during cattle raids. Further complicating the likely secession are the multiple tribes and internal feuding among the cattle herders.

South Sudan's army, or the SPLA, soldiers drive in a truck on the frontline in Panakuach, Unity state April 24, 2012.

SPLA (South Sudan People's Liberation Army) vehicles drive on the road from Bentiu to Heglig, on April 17, 2012.

Thousands of Southern Sudanese celebrate South Sudan's Independence in Juba, South Sudan, July 8 2011.

A worker lays out bags of grain at the Doro refugee camp in South Sudan, around 40 km from the border with Sudan, on Dec. 5, 2011

Refugees wait for food aid to be distributed in Yida refugee camp in South Sudan, near the volatile border with the north, on November 16, 2011.

A construction-company security guard walks by a new bridge on South Sudan's Juba-Nimule road on Jan. 24, 2011

A man waves South Sudan's national flag as he attends the Independence Day celebrations in the capital Juba, July 9, 2011.

Sudanese celebrate in Juba following the announcement of the preliminary results of the South Sudan referendum on Jan. 30, 2011

South Sudanese wait to be transported on a train from Khartoum to recently independent South Sudan on October 28, 2011.