It seems that you do not understand historically, those japs tried many times to invade China:
Let me give you some example:
663 AD: Battle of Baekgang, Silla-Tang forces defeat Japanese-Baekje navy
1558 AD: Ming forces led by Qi Jiguang defeat Japanese pirates at Cengang.
1592 AD: When Japan invades Korea in the Imjin War, Ming China aids Korea with troops and supplies.
1894 AD: japs invaded korea, attacked china navy and grabbed taiwan from China
1932 AD: Imperial Japanese colonialism in Manchukuo
1931 AD: japs invaded northeast China, the 9/18 invasion
1937 AD to 1945 AD: japs full invasion into whole china
You see, before 1894, China has always defeated the invading japs. However, after two opium wars, so many rebellion wars within China, Qing dynasty finally had drained its own power to defend itself. After its collapse in 1911, China has fallen to such a stage of constant in-fights, warlords controlled different regions and the whole country fell into pieces. That gave those japs perfect time to grab China. In that time, even Chiang could not control all of the armies since a lot of them gave their loyalty to their warlords, not Chiang. That is why so many cities fallen to the invading japs. There are reasons for that: for example, much worse weaponry, poor trained soldiers, few strategies, and etc. However, one important reason was that those warlords did not want to sacrifice their own forces to defend those japs. That was also why they would rather retreat to keep their own force but for defending the country.
So I do think those japs will do such invasion again. japan is such a smaller island with huge population and so few resources. For its own survival, invasion is the best solution.
I am happy to hear your kind words for the man who is portrayed as a symbol of Sino Indian Relationship.
But do you think even if China becomes weak in the future(which is not possible) that Japan will attack a nuclear armed China.
I don't think so. The next time a global war errupts for sure its going to be man vs machines.