25

Put Guderian in charge of the invasion of France and let him handle things. Don't interfere or tell him to halt the advance under any circumstances. If the UK offers a negotiated surrender, take it. Also, don't attack Russia. If you absolutely cannot resist attacking Russia, then be patient; don't do it until after France and the UK are defeated. Again, don'...


13

Your Enigma isn't as secure as you think. (Followed by: let me explain public key cryptography to you). The allied forces had a significant advantage through code-breaking while the Germans considered it unbreakable. Whether you know or are unaware of the coming ATTACK AT DAWN, this may eventually turn things around. It's your story that makes this work :-)...


13

Don't fight a war on two fronts. The obvious answer is that the German resources were stretched by attacking Russia while it was pushing into France. On top of it all, they attacked at a point when all the Russians had to do was keep them outdoors during a Russian winter and let many of the enemy soldiers die. Is it possible Russia would have attacked ...


10

No information would help Nazi Germans to win the war - only to avoid it, like fascist Spain did. My first argument - Nazis are Nazi, you can't make them "softer", and they did the best they could Long term war was not a German choice. They planned to end the war with Russia at the end of summer of 1941 (and they almost did it!) and to conquer all "living ...


9

First of all this isn't, strictly speaking, a case of retro-causality, it's simply a standard piece of time travel. There are three possible general solutions to explain how this can happen. Each solution depends on the nature of time. And, yes, each solution has its own nature of time. You can think of them as different models of time and causality. You ...


6

I believe that you're misunderstanding how this works. Or, misunderstanding how people understand how this work, I'm not sure there's a practical difference when discussing theoretical concepts like this which probably can't ever occur. Anyway, to quote you: The event is called “retro-causality” or “backward causation” on Wikipedia. But the bottom line ...


6

Likely not much, if at all. It's not like you could look at a piece of metal from the future and figure out how it was made. If you took an iPhone back to 1995, they would probably be able to figure out what it was doing, but the ability to manufacture a processing chip that small would still require a decade before the first iPhone and two before modern ...


5

It won't help you for anything outside of local events. Light travels at 1 foot per nanosecond so converting to microseconds that limits you to events that occur within 50,000 feet (15 km). Anything further away and you may know about it early, but your response to it won't be faster than actually being there. Besides this, you will have to deal with ...


5

The short answer is that there isn't a sane scientific explanation to what you're proposing because it's impossible, even if time travel was indeed possible. These kinds of 'kill your grandfather' paradoxes would break everything we know about the universe to date. On the one hand, being able to do this would be good news because it means that the universe ...


3

Knives. Compact, so you can bring all that the store has. Compact, so you can hide them on your person and move freely. You can cache some for later retrieval in case you are robbed. Useful. The utility of a knife like this is immediately evident to anyone, regardless of station in life, and even if they cannot read that it is a utility knife. On ...


3

Not really "before WW2 begins" but during the war could reveal things like opponents movements and supplies. If he knew which battles to avoid/write-off, which supply routes were vulnerable, and the advice not to invade Russia could have done a lot to avoid wasting resources and being more effective in dominating. Also, location of various manufacturing ...


3

Just hand them the history book They don't need technical information, access to the 20/20 hindsight that we have available would be enough to change everything, and if they don't take that hint there's no helping them. There were many mistakes made by all sides in the run up to, and during the war. Given access to that information, advance knowledge of D-...


2

As far as what would actually happen in the real universe, we cannot know without a working time machine to experiment with. As for time travel as a fictional plot device, the best explicitly stated model I have seen is in Eliezer Yudkowsky's "Harry Potter and the Methods of Rationality", Chapter 17 "Locating the Hypothesis". (I hope it's okay to reference ...


2

"Sufficiently advanced technology" This looks to me like an example of Clarke's third law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong. The only way of discovering the limits of the possible is to venture a little ...


2

You would have to assume a rational German leadership that was willing to act on the advice. If there had been such a leadership, wouldn't they have listened to the German advisors who would have argued against two-front wars, declaring war on the United States, and so on? I don't think there are simple one-paragraph pieces of advice that could make Germany ...


1

If you get to him early enough, have him plan an intelligence operation to assassinate Chamberlain between September 1, 1939 and October 1, 1939. Although Churchill's later conduct of the war as Prime Minister was admirable, in the winter of 1939-1940 his suggestions as a member of the war cabinet were, in retrospect, insane. Churchill states in his memoir ...


1

This question probably requires you to compile multiple answers, as Germany really had a lot of problems it had to defeat to win the war. From resources to production to tactics and treatment of populations. You could tell them how the UK will beat Enigma, and then change a lot of codes and how it works. Additionally you could tell them how compromised ...


1

It might have been too late in 1939 when a lot of scientists had already left, but it might be very useful to focus on nuclear weapons if you go back a little further. Germany had the relevant knowledge at the time, and the Manhattan project took just 4 years, so it seems conceivable that Germany could've nuked other countries into surrendering before those ...


1

Considering that Hitler was overconfident in his own military expertise the best advice would be: Let your generals do their job, and stay on the balcony to do the crowd preaching. A country like Germany, dependent on import for supplies, cannot sustain a long term war. It is forced to proceed with small and temporally short jumps. Cutting off all import ...


1

It depends on the shape of space-time. If space time is fully deterministic and time travel is a closed time-like loop, what you describe isn't possible. There are two ways for it to not be possible; one is good news, the other is bad. If we don't have closed timelike loops from time travel, either the "sending" future exists independently of the past it ...


1

I'd be very worried if my pacifist programmer friend was sent in the conditions you describe during the war. He would have to be extremely fast at proving he (and only he) can provide significant help to the country. Well, either extremely fast OR in a way that puts him in a situation of power. Read "blackmail the authorities of the country". Not to extort ...


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