What were the most significant military blunders committed by Germany
during World War II?

Invading Russia in 1941.

Not invading Britain in 1939/40.

Geof, 

While it is perfectly true that Britain was ill prepared to withstand
a German invasion in 1939/40, Hitler was also ill-prepared to launch
an invasion.

The Germans had mainly slow-moving barges for transporting their
troops and the English Channel is not an easy crossing if the weather
is unfavourable.

In any event, Britain had radar and an effective Air Fighter force
that had hurt the Luftwaffe in the Battle of Britain.

Had it come to an invasion, Hitler would have been betting on good
weather, which is a lottery in September when the invasion force was
being readied.

Although Hitler was an out-and-out gambler, I would argue that he took
the sensible option of not invading Britain at that time, particularly
as he was still hoping to do a peace deal.

uh oh .. I detect a 78 comment deliberation .. taking the back stalls,
just throwing Jaffas down the aisle here.

Starting the darn thing in the first place.

If the Germans had built a strong manufacturing base, from that become
a 'recognized' financial power, pandered to the French, established a
few Iron and Coal treaties, brought in a few satellite states to add a
'Southern European' element, then they could have /bought/ as much
Lebensraum as they wished.

It is nice to see people learning from their mistakes.

Many historians consider that Germany's declaration of war on the U.S.
after Dec. 7, 1941 was a huge blunder, as it committed American troops
to a European invasion.  American resources devoted entirely to a war
with Japan would have had a markedly different outcome, even though
the U.S. would have been a tacit supporter of the United Kingdom.

Best regards,

Omnivorous-GA

'Starting the darn thing in the first place' was a POLITICAL mistake.

You can always trust the politicians to make the MEGA mistakes.

Please don't blame poor Adolf for any of his military mistakes.

After all, he was only a Corporal.

Could Corporal Barbarelli have done any better?

'Many historians consider that Germany's declaration of war on the U.S.
after Dec. 7, 1941 was a huge blunder ...'

Hmmmmm .... ANOTHER Political Mistake.

Agreed?

The following Hitler blunder pertains to D-Day in Normandy and
Hitler's steadfast belief that the invasion was only a
diversion....the main attack(s) would come elsewhere.

I speak of Operation Fortitude, the daring agent Juan Pujol Garcia,
British Intelligence code-name, "Garbo", Abwehr Military Intelligence
code-name "Arabel", and a triumph of imagination.

Calling it a Hitler military blunder does not diminish the Allied
success in creating the conditions for Hitler's D-Day blunder.

http://historynet.com/wwii/bldoubleagent/index.html

Yes, grthumongous-ga ...

But it wouldn't have mattered.

If D-Day had been a disaster, we'd have got him anyway. Remember the Atomic Bomb?