[ccday]

This is purely my opinion: Lincoln’s point was that the threat of civil war or violent dissent (what we today would call domestic terrorism) is a much greater threat to the US than foreign states. I think this remains true today. In fact, what you mention when you say a fracturing of states within was exactly what he was talking about.

A foreign state would need to cross the Atlantic ocean, contend with the most powerful Navy on earth several times over, land in either Canada or Mexico, both of which are US allies, and then mount a land invasion on the US homeland. It’s hard to imagine how that would be possible.

You raise a good point when you say crushing defeat does not necessarily happen on the conventional battlefield. Nuclear weapons create the possibility of MAD, and other “battlefields” like the cyberspace or global economic warfare have developed since Lincoln’s time. I still think the essence of what he said is true though: the greatest threat to the US comes from within.

[vba616]

Drones will change things before long.

I'm thinking of

https://en.wikipedia.org/wiki/Fu-Go_balloon_bomb

almost forgotten, but how different it would be if they were intelligent.

Talk about an amazing coincidence:

"On March 10, 1945, one of the last paper balloons descended in the vicinity of the Manhattan Project's production facility at the Hanford Site. This balloon caused a short circuit in the power lines supplying electricity for the nuclear reactor cooling pumps, but backup safety devices restored power almost immediately."

[nautilius]

How would smart balloon bombs make the U.S. more 'invadible'?

[vba616]

Not literally balloons, but guided drones generally. They would make the US "more invadable" by being an invasion. Think about it being just a constant for years, and disrupting American society kind of like covid. People would have to change their lives, consider everything in relationship to defense, even if there were few casualties. It would be demoralizing if most of the existing weaponry was no use.

I haven't gone out of my way to familiarize myself with the perennial rocket launches at Israel, but that's the general sort of thing I'm picturing. Harassment that would demonstrate people are never safe, while not rising to the level where the international community would accept massive retaliation.

[nautilius]

How are drone attacks an invasion? So from your own argument, do you consider Israel an occupied country because rockets are constantly launched at it? How about London during the Blitz? I don't think either group would ever consider themselves having been 'invaded'.

[vba616]

In both cases, the rockets weren't/aren't guided precisely and can't loiter, right?

And in any case, Israel is used to it and used to having missile defense, and is a very small country. Nobody expects that any part of the country is far away from the borders and enemies. Whereas it would be a sea change for the US, if attacks could occur anywhere, and psychologically it would be like an invasion.

I'm using "invasion" loosely to mean an attack that reaches inner areas that people take for granted are safe, not necessarily boots on the ground.

[nautilius]

Sure, if you define 'any attack whatsoever' as 'invasion', then, of course -- according to your own definition -- any attack is an invasion. Just doesn't mean anything anymore.

[b112]

Lincoln’s point was that the threat of civil war or violent dissent (what we today would call domestic terrorism) is a much greater threat to the US

Which us why those which dislike the US's place in the world, focus so much on fanning any flames of discontent, or political differences they can.

[bshipp]

Agreed. Even when the forces were more balanced and Hitler had declared war on the USA the German army never stepped foot on the lower 48. the closest they got a few uboats picking off merchant shipping but even that was pushed back after a few months of horrendous American losses.

I'm truly surprised Hitler never tried some sort of guerrilla attack with a small force just to cause chaos and terror in the heartland. it's not like the USA was very well defended at all from any sort of coordinated landing back in the early 40's.

[dugmartin]

There was a rather incompetent attempt that was quickly rolled up: https://en.wikipedia.org/wiki/Operation_Pastorius

[BlueTemplar]

By the point the USA declared war, he had basically just lost the war against the USSR (as it's in those days that his Blitzkrieg definitely ground down, in visual sight of the Kremlin, to add insult to injury). So he just didn't have anything to spare for such an attack.

[vba616]

Hitler made the rather peculiar decision to declare war on the US first, a few days after Pearl Harbor.

Supposedly it was pointed out that their agreement for mutual defense with Japan didn't require them to declare war if Japan was the aggressor. But that was ignored.