When the Soviet Union placed nukes in Cuba, why did the US react as aggressively and nervously as it did? After all, the nukes were harmless to the US internal security. They were there to contain the US external influence against Cuba. When has Cuba ever threatened internal security of the US?
Jokes aside, I am not sure whether you are being genuine or being difficult on purpose. Any country that has spare resources will try to create a buffer zone around itself in order to counter possible future threats. It seems self-explanatory. American military is in the region doing the same thing - building a buffer zone around China. I think Americans refer to it as "containment", but it's literally the same concept.
Jokes aside, I am not sure whether you are being genuine or being difficult on purpose. Any country that has spare resources will try to create a buffer zone around itself in order to counter possible future threats. It seems self-explanatory. American military is in the region doing the same thing - building a buffer zone around China. I think Americans refer to it as "containment", but it's literally the same concept.