The territorial disputes involve nearly a dozen countries in at least three major seas, and they have set off a chaotic crisscross of conflict in some of the world’s most trafficked shipping lanes. The disputes are not all connected, but analysts say that several of Asia’s key countries — China, Japan, South Korea and the Philippines — have in recent months followed a similar pattern, turning old historical squabbles into national priorities, escalating tensions and raising the chances of a small-scale armed conflict.

The countries are driven to claim these far-flung offshore territories in part because of their growing need for the oil and gas reserves in the waters around them. Japan fears prolonged energy shortages as it turns from nuclear power, and China, already responsible for one-fifth of the world’s energy consumption, is racing to increase its share as its economy modernizes…

The countries are also driven by fierce, though sometimes small, nationalist movements in their own back yards. The nationalism has been intensified by social media, some analysts say, particularly in China, where hundreds of millions of Internet users can share their opinions and public sentiment is harder than ever to ignore. Countries such as South Korea and China are set for leadership changes this year, making government officials wary of backing off claims and appearing weak.