I think it will revolve around 3 things
1: China's quest for resources
2: The on-going Arab-Israeli problem
3: Frustrations with the UN
The two will tie together, as i feel that it is inevitable that Israel "crosses the line," at some point. They'll come up with a radical solution to some sort of problem which the major middle eastern powers will find intolerable, and these powers will overlook their differences and form a security pact to put a stop to Israel's next move. A security pact of Iran, Iraq, Syria, Lebanon, Jordan, Egypt, Libya, and Pakistan.
Iran utilizes the security pact as an excuse to begin moving radical islam all over the region, creating a broader security crisis, especially in places like Central Asia and Turkey
The West (including Russia, who has a vested interest in combating radical islam), will vehemently protest this through the UN Security Council. China, seeing a slam-dunk opportunity to negotiate access to massive oil resources, vetoes the measure. The angst is turned against China for "abusing," their status as a Security Council member, and the General Assembly, eager for reform to the old Security Council system anyway, revokes China's status as a permanent member.
China interprets this action as further western exclusion from the power structure, and so breaks off normal relations, leaves the UN, and begins solidifying relationships with the Mid-eastern security pact. These nations also leave the UN, as well as a set of other "rogue nations," that have been aligned with China in the past, and have been "pushed around" by the UN before, nations like North Korea, Vietnam, Laos, Myanmar, the Sudan and Serbia
The Chinese also see a great opportunity to upset America, and negotiate a pact with Chavez's Venezuela, a move designed to provoke the US. Cuba, very much afraid of a general US retaliation against threats in the region, quickly moves to join this pact.
Iran is the final aggressor: fearing the existing US military threat in neighboring Afghanistan, they begin moving troops in to support the Taliban and to negate that threat, and everything just sort of spirals out of control from there. The major western nations that fight in the name of the UN are: America, Britain, Russia, Israel, Canada, Brazil, Germany, Italy, France, South Africa, Greece, Poland, Turkey, India (who's really just in it to fight Pakistan), Australia, New Zealand, and Japan (who uses this whole event as an excuse to get a real military back up and running)
Monster Hunter: pissing me off since 2010.
