In the post "The Third Sphere" I talked about two new factors destabilizing the known pattern of seldom wars with long periods of peace between. They are:
1) IT warfare and 2) two-sided interventions in important North hemisphere countries.
The last of these points may be generlized to also include conflicts like the one in the South China Sea. It would then be formulated as two-sided interference in areas which by one side with or without right are seen as essential to its vital interests. This is in its turn with or without right challenged by the other side.
In the modernity of our Western civilization this phenomenon has typically occurred after periods of stability in the northern hemisphere or rather the richer world, the great powers and their satellites. In the first 5 decades after WW2 the USA and the USSR, NATO etc. and WAPA. The stability was based on mutual respect on spheres of interest and rules for behavior. This was also the reason for the lack of destabilizing effect of the interventions in Hungary 1956 and Czechoslovakia 1968. Of course the mutual acceptance of legitimate interests did not involve the Third World.
The kind of destabilizing conflicts with interventions in contended areas typically comes after events which change the political landscape. Such developments lead to unclear borders between the spheres of interest and thus makes it possible to challenge these borders. A classical event was the Cuban Revolution which moved a Caribic island out of the American sphere. The Soviet intervention with employment of nuclear missiles in the American backyard followed. Kennedy had to intervene, and fortunately the destabilizing effect was stopped quickly with a redefined border between East and West with new specific rules for conduct. Thus the episode did not alter the overall picture.
A far deeper change of political landscape came from the fall of the USSR with the independence of both East Europe and former Soviet republics. Russia suffered a very significant reduction in controlled areas. This meant that new definitions of spheres of interest were needed, but till now there certainly has been no such agreements. Obviously the problems with two-sided interventions in Ukraine stems from here.
The rise of a new country, China to a world power is another way the political landscape can change. A new big power claims its own sphere of interest. In this case including the South China Sea. If this is challenged by the United States, we have a conflict of the same type as the one in Ukraine.
It must be stressed here that I am not siding with any country in these analyses.
As said conflicts of this type are a new destabilizing factor in int'l politics, just like Cyber-attacks are. They should be contained. Ideally there should be no spheres of interest outside the big powers. Each smaller country should be fully independent. But things do not work this way. As often said many small countries are not any longer fully independent.
In conclusion it would be desirable to have mutual three-sided agreements between the United States, China and Russia on spheres of interest and on conduct to preserve stability and predictability.