Uganda's neighbor to the north, Sudan, has been at war with itself for since 1956. After decades of fighting for independence from the north, southern Sudan seceded last year in July and became the Republic of South Sudan, six months after nearly 99 percent of the region’s voters approved the split in an internationally backed referendum. The south’s departure did not put an end to conflicts though. Both nations face rebel movements within their own borders, and clashes along the new border are constant.
While the two nations continued to "discuss" how to make it work, a spreading rebellion inside Sudan prompted the Sudanese government to accuse the south of providing military support to the rebels. In November 2011 the president of South Sudan denounced the Sudanese government for threatening what he called a “military invasion” of South Sudan. He has accused the Sudanese government of bombing the South Sudanese areas and killing innocents and moving insurgencies on both sides of the border closer to an international conflict.
When South Sudan declared independence, it took billions of dollars’ worth of oil with it, gutting Sudan’s economy. Both sides desperately need the oil to run their governments, feed their people and stamp out insurrections. And theoretically, both sides need each other. The conundrum of the two Sudans is that 75 percent of the oil lies in the south, but the pipeline to export it runs through the north.
Here are a few more articles if you want more info:
Trying to live in the border between North and South
No longer citizens
On the brink of war
What life is like for Southerners stuck in the North