In the anarchic world of international politics, nations always prefer having buffer zones whenever there is a presence of a big enemy in the vicinity. This gives them the much-needed space and time to prepare its defence in case the enemy makes a threatening move.
The grammar of security mechanism in international relations attaches a prominence to the concept of ‘buffer zone', hence.
In the colonial era, Afghanistan was held as a buffer zone by the Britishers against the imperial designs of Russia. In the current times, Ukraine serves as a buffer between Russia and the West.
Buffer zones have proved in the past that they are indeed significant to prevent the worst-possible consequence in world politics, which is war. Hitler's attack on Poland, a buffer between the Natzi Germany and the erstwhile Soviet Union had flagged off the devastating Second World War.
The volatile continent of Asia is witness to two important regional theatres that have a buffer state and the slightest of impact on the balance of those buffer zones could pose a big threat to the regional peace. Moreover, the funny part is that one state is party to the buffer scenario in both regions and has opposite experiences in dealing with it.
In East Asia, China considers North Korea as a buffer between itself and its traditional enemies in the region, including the outsider: the United States. The fact that North Korea harbours similar sentiments vis-à-vis China's opponents serves as a boon to Beijing and it backs Pyongyang in its bigger design of strengthening its defence, particularly against the US.
Whenever it is said that Beijing hasn't been successful in reining in North Korea's dangerous ambitions, the former says the hostile stands of the US, Japan and South Korea have allowed North Korea's belligerence to continue.
In South Asia, China is at an advantage over the buffer
In South Asia, similarly, Nepal serves as a buffer, more for India against China. Given Beijing's ill-fame as an expansionist power, it is in India's own defence interest that it has always maintained a good relation with Nepal, even though the latter has played the China card conveniently (whether the monarch or the Maoists) to create pressure on India.
There have been low phases in India-Nepal relations that have made China interested (it has a diversity of interests---political, ideological and strategic---to act in Nepal) but New Delhi has always tried to maintain the small Himalayan neighbour as the second line of defence against the Chinese whose gobbling up the Tibet had far-reaching consequences in world politics.
In East Asia, the buffer has backfired
However, while China had a happier experience with the buffer politics in South Asia, it is not having an ideal outcome with its North Korea plan in the Far East.
In South Asia, the serious differences between India and Nepal over the latter's newly promulgated constitution saw the latter getting closer to China at the expense of India, who was also accused of imposing a blockade worse than that of the late 1980s to cause immense hardship for the common Nepalis.
It was more than a good news for the Chinese.
But in East Asia, North Korea's reported testing of the powerful Hydrogen bomb has left Beijing in a spot of trouble. Pyongyang has not only snubbed its biggest ally through the act, it also raised problems for Beijing by drawing the attention of the entire world to the region, something which the latter hates.
The belligerence shown by North Korea would see the US and others retaliate in varying ways (Washington has already deployed the B-52 nuclear bombers over South Korea as a response to the January 6 test by the Kim Jong-un regime) which would ultimately add to China's isolationist stand on the Asia-Pacific.
Even taking a stand against North Korea is not easy for the Chinese (just like for the Indians in Nepal because of the geostrategic stakes) for in that case, the hermit kingdom might implode under multi-layered attacks, putting China's borders under threat.