NAIROBI, Kenya — As many had predicted, the independence of South Sudan has triggered conflict.

But few could foresee the complexity of the battle. Fault lines have developed not simply between the diminished Sudan and the newly independent South Sudan.

In South Sudan there have been attacks and clashes as well the depressingly routine cattle-raids in which scores of people are regularly slaughtered. But it is north of the still-disputed border, in Sudan, where many key changes are occurring.

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There is now an almost-contiguous arc of resistance to President Omar al-Bashir’s regime stretching across the country from Darfur in the west, through the disputed territory of Abyei, across the Nuba Mountains of South Kordofan and into Blue Nile state in the east.

This string of rebel opposition to Bashir is the most concerted challenge yet to his 22-year rule.

All the anti-Khartoum rebels say they want more or less the same thing: to get rid of Bashir and his Islamist regime, and replace it with a government that is more inclusive and democratic.

There is a unity — at least for now — among Sudan’s many rebel groups. That unity took more solid form with the formation of the Sudan Revolutionary Front (SRF) last month. The first point on its manifesto read: “We affirm our resolve to overthrow the National Congress Party (NCP) regime using all available means, above all, the convergence of civil political action and armed struggle.”

It said it would appoint a "Joint High-Level Military Committee" that would bring together the commanders of the Sudan People’s Liberation Movement-North, the Justice and Equality Movement and the two branches of the Sudan Liberation Movement/Army.

Navigating the various rebel groups gets a bit "Life of Brian" — People’s Front of Judaea versus the Judaean People’s Front and so on — but it is too early to dismiss their proposed union, not least because Bashir appears weaker now than at any time in his rule.

Bashir is reacting with military attacks on the various groups, and he is attacking civilians as well as rebels, as he has done in Darfur. But Bashir's use of force now appears to stem from weakness more than strength.

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The splitting of Africa’s largest country severely — perhaps even fatally — undermined Bashir’s position. He has ruled with a iron, often brutal hand, his authority deriving directly from his Islamist posturing and military strength.

Bashir's willingness to resort to violence has earned him an indictment from the International Criminal Court (ICC) in The Hague and the distinction of being the world's only head of state to be charged with genocide while in office.

Bashir’s problem is this: What happens to authority that rests on strength when that strength is thrown into doubt? The North did not lose the civil war against the South, but after 22 years of conflict, it did not win either. Yet the 2005 Comprehensive Peace Agreement opened the door to the South’s independence.

This year, at the ballot box rather than the barrel of a gun, Bashir lost the South. With it went some of his authority and much of his economy.

Most of Sudan’s oil lies south of the border and how that wealth — valued in the billions of dollars — should be shared is at the core of bad North-South relations that have existed since July.

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Bashir is facing a perfect storm that threatens to unseat him, and it originates in his old enemy, the South. The loss of the South's oil fields has decimated the North’s economy. In addition, South Sudan’s independence has emboldened his armed opponents in the remainder of Sudan, and the Arab Spring has further encouraged his civilian opposition. Further, the loss of a vast chunk of Sudan has given the lie Bashir's reputation for unassailable military strength.

Bashir is far from defeated, as his army’s attacks on rebels and the civilians among whom they live make clear, but his days are, perhaps, numbered. And this spells a torrid time for both Sudans.