Before anyone starts marching...
...there will be large scale fear worldwide. A major city was just destroyed by causes unknown. Was it some super-weapon, either one that A/H was working on and malfuncioned, or an enemy's. Could it be the wrath of a diety? Could it possibly be something from space? There will be worldwide panic, and possibly a depression.
Even if the scientists determine what happened with some condifence, the general public might not be reassured. For that matter, some may say that the meteor was still divine vengance for one thing or other.
If it was a meteor, are there more on the way? The scientists will have no way of knowing.
Einstien published his theory of relativity in 1905--thus showing that mass and energy can be changed into each other. Perhaps the explosion such a conversion.
In short, althought the Empire is probably in deep trouble, I doubt that anyone will be marching anywhere very soon. The last thing to do is kick off a major war when your own future is uncertain.
Longer term, the loss of a major city will make some want to make sure that this doesn't happen again. Once the conclusion "meteorite" is reached, I espect to see a lot if interest in asteroid hunting. In addition expect that, as soon as it's realized that there's a way to get up there, there will be attempts.
Perhaps, in 1945 or so, the rocket ship "Vienna's Ghost" takes the first man into space.
Sadly, there will also be a desire to posess the means of destroying a city on demand--another reason to get into space--until someone splits tha atom, and discovers that it may be possible to make big explosions wothout moving really big rocks.
Just a few random musings...