It is instructive that so close to the anniversary of American independence is another anniversary much more somber in nature. To be specific, today is the seventieth anniversary of the battle at Marco Polo bridge in Beijing. This incident was the final straw in the long history of Sino-Japanese irritants, and led to open warfare between the Empire of Japan and the forces of Revolutionary China (led by Chiang Kai-shek's Kuomintang Party, or KMT).
As a result of the battle, China and Japan were engaged in full-scale war, as opposed to the mostly diplomatic battles they had engaged in since the end of the previous war in 1931. This war continued until Japan surrendered to the United States and the remainder of the Allies in 1945.
One side effect of the war was to allow Mao Tse-tung's Communists to grow strong as the Nationalist Party (KMT) focused its energies on fighting the Japanese. The Chinese Communists and Chiang Kai-shek's KMT were deadly enemies, and in the years leading up to the battle at Marco Polo Bridge the KMT had forced the Communists to retreat in the famous Long March, greatly weakening them. Chiang intended to destroy the COmmunists before taking aim at the Japanese. However, this policy was not shared by all of his supporters. In fact, Chiang Kai-shek was actually kidnapped by Marshal Zhang Xueliang in order to force him to agree to put resistance to the Japanese as his first priority.
Chiang did agree to focus on defeating the Japanese, but at the cost of allowing the Communists (who did virtually nothing against the Japanese) to grow strong. In fact, they grew strong enough that at the end of World War II, they were quickly able to defeat the KMT and seize control of China, although it ought to be noted that they were aided by the corruption and elitism that was prevalent in the KMT as well. Had Chiang been willing to consider land reform, he might have managed to defeat the Communists despite their strength. So in one aspect, the battle at Marco Polo Bridge was an important step on the road to China's submission to the bloody hands of the Communists under Mao Tse-tung.