September 17, 1939. You're Ignacy Mościcki and You've Just Been Informed a Time-Traveler Has Arrived From the Future.

@SomeMichGuy
...he'd learn that 1/5 of the population of his nation would be killed in the war.

Dropping the bomb on Nazi Germany would likely cause Stalin to hit the pause button.

The USSR within a few months had difficulty just in taking on Finland. They were in absolutely NO POSITION "to take over much of Europe in September 1939."

It would almost surely have caused the German military to overthrow the Nazi government.

@beckyromero Thanks for the info; I'll have to look more closely at that.

It's my guess that a guy willing to let 20 million of his people starve (Stalin) would be happy to use them as fodder...and if he could take fields and factories...he'd come out ahead.

If Berlin had been bombed somewhere over the Reichstag, followed by, say, Essen or shipyards/docks, there would be at least a few major areas of questions

1) Where would the military planners/heads have been? If mostly in Berlin, are there people left who could effectively do as you suggest? And what they were thinking in Sept. 1939 v. late 1944/1945?

2) Remember that the use of the bomb on Japan shocked the psyche of the Japanese. What if the same happened to Germany? A dazed, undirected Germany is very different from a clear, directed Germany. There could be an opportunity for France, Britain, for the USSR, etc., to try to move on and take assets from a Germany in shock...or at least try to destroy, say, the Krupp arms works, shipyards, etc.

3) If Germany *were* in shock, with the top heads of the Nazi monster destroyed, would the government even exist or continue?

Speculating is intriguing by far from certain.

@SomeMichGuy

There were enough high-ranking officers in the Germany military who would have been in a position to overthrown the Nazi government. They would not all have been in Berlin. And Berlin need not necessarily been the target of a Polish nuclear attack.

France actually briefly invaded Germany in the west. With a nuke dropping somewhere in Germany and the Allies invading from the west, the Nazis would have been, well, kaput.

An immediately threat of a nuclear missile attack on Moscow or St. Petersburg surely would have given Stalin pause and time for the Polish army to re-deploy troops to the eastern front.

The Soviets in September 1939 were in no position to take on the Poles, French and Brits. They had their hands full in a few months with just the Finns.

@GlueGun lol Yes, but read the OP's background.