China knows less about and has less influence over its close ally North Korea than is usually presumed and is likely to eventually accept a reunified peninsula under South Korean rule, according to U.S. diplomatic files leaked to the WikiLeaks website.

The memos — called cables, though they were mostly encrypted e-mails — paint a picture of three countries struggling to understand an isolated, hard-line regime in the face of a dearth of information and indicate American and South Korean diplomats' reliance on China's analysis and interpretation.

The release of the documents, which included discussions of contingency plans for the regime's collapse and speculation about when that might come, follows new tensions in the region. North Korea unleashed a fiery artillery barrage on a South Korean island that killed four people a week ago and has since warned that joint U.S.-South Korean naval drills this week are pushing the peninsula to the "brink of war."

The shelling comes on the heels of a slew of other provocative acts: An illegal nuclear test and several missile tests, the torpedoing of a South Korean warship and, most recently, an announcement that in addition to its plutonium program, it may also be pursuing the uranium path to a nuclear bomb.