Why is the German Invasion of Poland usually marked as the beginning of the Second World War?

Jan 2015
3,360
Front Lines of the Pig War
#42
No combat involving British or Commonwealth forces, or outside Europe happened in 1939.
Beg to differ.

One of the first actions in the war was the Panzerschliffe Graf Spee raiding the Indian Ocean, where it sank the tanker Africa Shell on Nov 15, 1939. Royal Navy attempts to hunt down the raider in the Indian Ocean were unsuccessful.

The Battle of the River Plate (South America) occurred in Dec 1939.
Battle of the River Plate - Wikipedia
 

Naomasa298

Forum Staff
Apr 2010
35,031
T'Republic of Yorkshire
#45
Beg to differ.

One of the first actions in the war was the Panzerschliffe Graf Spee raiding the Indian Ocean, where it sank the tanker Africa Shell on Nov 15, 1939. Royal Navy attempts to hunt down the raider in the Indian Ocean were unsuccessful.

The Battle of the River Plate (South America) occurred in Dec 1939.
Battle of the River Plate - Wikipedia
Either of these in September 1939?
 

Maki

Ad Honorem
Jan 2017
3,386
Republika Srpska
#48
Why is it so important that it happened in September 1939? Britain declared war in September, any subsequent clashes between Britain and Germany were a result of that declaration which happened in September.
 

Naomasa298

Forum Staff
Apr 2010
35,031
T'Republic of Yorkshire
#49
Why is it so important that it happened in September 1939? Britain declared war in September, any subsequent clashes between Britain and Germany were a result of that declaration which happened in September.
If you're going to claim it involved all of those countries, and that is what justified calling it a World War and the September start date then clearly, it IS important it happened in September.
 

Maki

Ad Honorem
Jan 2017
3,386
Republika Srpska
#50
If you're going to claim it involved all of those countries, and that is what justified calling it a World War and the September start date then clearly, it IS important it happened in September.
Were all those countries at war with Germany in September 1939? Yes. Did all those countries actually start mobilizing armed forces to fight Germany? Yes. How were those countries not involved then?