Biggest military upset ever?

[OSR stands with Israel]

I'm not comfortable with 'upset' as that's using the language of sport and that's just not appropriate. Though very few events in all Military History have been as utterly shocking as the Fall of France, that's true enough.

The outcome wasn't shocking at the time, theoretically Germany would have beaten France at any time on a straight one to one, and there was no french-russian alliance, french morale was always low in the run up to that war for those reasons.

It was the speed, although wars always tend to be fast moving when they begin and end.

In WW1, it would make full sense for Germany to have beaten France in a 1 vs 1. However, in WW2, it would not have made sense, as France was much stronger all around as of 1940, yet it lost anyways due to sheer incompetence.

France was far weaker in 1940 than in 1914.
WW1 France was called the "Arsenal of Democracy" because they became the bulk of allied war production and manpower, by WW2 France was bankrupt and had a manpower shortage.

Germany was far stronger in 1940 than in 1914.
They absorbed the best bits of the old Austrian Empire and had solved the agricultural crisis that plagued the Central Powers during the blockade of WW1.

Ideology also played a role, unlike in WW1 a lot of frenchmen looked upon Hitler as their ideological leader, while the Kaiser was just a generic king, so french patriotism was weaker.

Germany was not stronger in 1940 than they were in 1914 , its just that the French resolve to fight was far less in 1940 than 1914 and they were not fighting a two front war in 1940 unlike 1914.

Keep in mind that Germany nearly made it to Paris in 1914 despite the fact that France was extremely resolved to fight and they were already fighting a two front war by then