German invasion was called Krigsfall I ("war case I") and was considered the most likely one during WWII. All contingency planning for Krigsfall I was dropped around 1950 and all planning was focused on Krigsfall II (Soviet invasion).

Krigsfall III was the WWII planning against the very real risk of British invasion, and post-war this was redefined as an invasion by Britain/US, US/Britain or NATO. Almost no planning was done until the last 80's, when some low prioritized planning was done on Krigsfall III which was then seen as an invasion from Norway (by either NATO or the Warsaw Pact).

Or maybe by the nasty Norwegians themselves... ;)

One important reason so much focus was on Russia pre WW1 was that they were not only the last ones we had lost a war against, but before that war we had fought a number of wars against the Russians during the 18th century, including the Great Nordic War.

We also, very importantly, shared a land border, while ze Germans would have had to defeat our Navy before they could invade, something which would have been a bit challenging before Germany was united in 1871. Another important reason was that Sweden and Germany where very close culturally; if we would have had MTV in Sweden 100 years ago, they would have sung in German, not English.

That was further strengthened by the common perception of Russia as the Threat.

Peak oil is not an energy crisis. It is a liquid fuel crisis.