[credit_guy]

> So the lesson here would be: Donʼt start a war, you have to wait until you can credibly claim to be attacked; wage war from the position of the defender.

No, not really. The real lesson is: Win the wars that you start. Bismark did that, Putin is not able to. That's Putin's big mistake.

[Mlller]

No, Bismarck didnʼt, because he didnʼt start them (esp. not No. 1 and 3), and he could win them – among other reasons – because he didnʼt start them (that was the point about allies and benevolent neutral parties). As I said, this is often misunderstood, tragically so by William II.

[credit_guy]

In the case of Bismark, the allies and benevolent parties were not so because they were sold on Bismark's theater. They were so because of the cold calculus of self-interest. In the 1850's Prussia was seen as a second rate power, not that threatening. The other powers thought they have more to gain than to lose if Prussia nibbles at the expense of others. In 1870, Prussia was already dangerously close to being a great power, so France attacked. The other powers miscalculated, and thought that France being the bigger dog in that fight, it's not such a big deal if it gets a bloody nose. Few could foresee that Prussia will become the giant of 40 years later that could threaten pretty much all the others combined.

Before WW1 the calculus of war was quite simple:

  - Austria was on the decline. It was threatened by both Germany and Russia. They chose to ally themselves with Germany which they perceived as the lesser of the two dangers
  - Russia was growing. They were threatened by Germany. They allied themselves with France and later the UK in the Triple Entante. 
  - France was declining. Germany was their natural enemy, not amount of diplomacy could change that. On top of that, they still felt the sting of the 1872 defeat. 
  - Germany was growing. They were on the verge of becoming hegemon. They knew that France and Russia would like to attack it from both sides. They perceived that if they attack first, they stand a better chance to get a better deal in the end
  - UK was slightly on the decline. They used to be the undisputed hegemon of the seas, but now the new German High Sea Fleet was becoming a real nuisance. If Germany were to win the continental wars (like Napoleon 100 years earlier), they were going to be in big trouble. It did not take them long to figure out on which side they should fight (despite all the royal family connections).
  - the Ottoman empire. They were not a great power anymore. Still, if they perceived a threat, it was mostly from the Russian empire, which had had for about three hundred years the nasty habit to keep chomping at their territories

Putin's situation was much simpler. There are only 2 superpowers around, the US and China. The US will be against whatever adventure Russia tries. As for China, it will be ok with such adventures, provided they don't become a headache for itself. Putin did a pilgrimage to kiss the Sultan's hand, and that was that. He even went beyond the minimal task of securing China's approval, one way or another he also secured India's (tacit) approval.

[Mlller]

“[…] not so because they were sold on Bismar[c]k's theater.” Actually they were sold, and it wasnʼt just theater (‘this man means what he says’), but of course it was indeed the cold calculus of self-interest – that was one of the things Bismarck took into account in his complex calculus. And maybe we can even call it “theater”: in the sense a tightrope walk is, with which Bismarck compared the art of politics.

To be clear: I agree with your main point regarding the present war; I just think that specifically the “Einigungskriege” are not a good analogy, that they are quite unlike Putinʼs war, even before the question of defeat or victory comes into play.

You have shifted the focus to WW1, and I think your analysis of the power relations before WW1 is completely convincing (given the usual allowances due to brevity). (Nitpick: 1872 → 1871)