John Smith I wrote:

...

Anyway, you are correct, after the war the "big bubble" formed.

The time-line is something like this:

America declares war on japan: 12/8/41
German forces in Italy surrender: 4/19/45
Germany surrenders: 05/8/45
Japan surrenders: 09/2/45

Our whole involvement in the war (other than supplying
weapons/intelligence to our allies) is about 3 years and 3 months.

Rather amazing really, two nations beaten in a heartbeat, now we can't
even nuke one small middle east country, go figure. No men left like
that American president, military leaders and general population with
cajones ...

However, historians note a small increase in birth to death rates just
before or at the war start. Advancements in manufacturing,
transportation, cities, etc. are usually noted as the cause. How much
this all interacted with the war to increase population growth is still
debated in the halls of academia ...

Regards,
JS