I personally believe that while it could be seen as a "border dispute" in Poland, the reaction and promises of the other industrialized European nations (Britain and France) changed that aggression from local to global. This is NOT true in the Far East, first since there was no protection by other nations or promises to do so when Japan attacked a non-unified country (China). China hadn't yet resolved its own civil war, had no true central government, and had no guarantee from any another nation or set of nations to protect its borders. Poland did. This clearly shifts the "beginning" of WW2 to the European theater, not the Asian, the mid-east, the Horn of Africa, nor the Iberian Peninsula. It had become a "global war" in the Polish offensive, well before the Low Countries, the Danes, the Norwegians, or the French were invaded. Just my opinion of course, but the Sino-Japanese conflicts might well have petered out to nothing before 1941 if Germany hadn't gotten started in 1939 and signed pacts with the Japanese and Italians forming the "Axis" powers.