You should read up on what Chiang's strategy. He knew that Japan can no way take China quickly enough and that Japan was still too weak to defeat a major Western power. He realized where Japan had won in China in the past was because China kept trying to make peace after initial defeats so Japan was able to take China bit by bit. Based on this assumptions, his plan was to retreat into the interior, last as long as possible, and wait for aid from the Western nations.

A lot of history mocked Chiang but in the past two decades after China opened up the archives in Nanjing, Chiang has started to look much less of a fool but a strategist playing with a weak deck of cards. Counting on the Western powers was always part of his plan. He sent one son to Germany and another to the USSR as sort of "hostages". Stalin was a major supplier of arms to China for a while because Stalin needed China to occupy Japan's attention. Germany also ended up helping China by sending advisers to train the Chinese army (a big part of the reason why China lasted as long as it did and why the Battle of Shanghai stunned Japan.) At the same time Chiang sent his US educated wife to court the Americans. She actually got to testify in front of Congress to appeal for aid and her Southern accent was actually quite charming to some.

Not all wars are won on the battlefield (i.e. Vietnam War, etc.)