When discussing China's one-child policy, it seems the discussion usually revolves around the human rights violations and the dilemma of daughters, but I'm more curious about the cause. After watching a documentary and reading about Nanking, it seems the hit to the male population was enormous post WW2. Besides a cultural and economic favor for sons, was there also enough of a population imbalance for this to play a factor?
Edit: Loss as in human loss, not losing the war.
In short, No.
For starters, if you ask China, they didn't lose WWII. They were fighting against Japan, which was defeated and left the occupied areas, so they count it as a win. Plus the fact that "they" kept the mainland while the Nationalists were relegated to Taiwan…
But forgetting the outcome of the war and just focusing on what lead up to the creation of this policy, since the relevant factor is not who won but losses sustained in the fighting, and what happened next.
During the period following the war, mothers who gave birth to a large number of children were given an award, essentially a "Mother of the Nation" certificate. I forget the exact wording. This lead to an increase in population to make up for the losses during the war. China had a major population boom in the 1960s. The annual number of births was over 26 million for almost the entirety of the decade. In this period there were around 300 million births total, causing the total population of the PRC to be about 0.8 billion by the end of the decade.
It was at this point that the State decided it wasn't sustainable and started instituting family planning policies, but not to the degree of the one child policy. It was about a decade later, at the end of the 1970s, that such a policy was put into place. This is usually credited to Deng Xiaoping.
What ultimately lead to the policy was this:
A continually increasing population following the war
Lack of adequate farmland to support the population
concerns that the stress of such a vast population would ultimately harm the nation if not brought under control
Also worth note, but as a more recent development: Many developed parts of China now have the opposite problem. With an ageing population, places like Shanghai are trying to encourage couples to have more children, similar to the situation in Japan. Also, for what it's worth, the policy is not as strictly enforced as many believe, and if you're an ethnic minority, the rules are even less strict.