What was the apocalypse that preceeded Sora no Woto? The series Sora no Woto was based in a post-apocalyptic world that significantly reduced the technological capability of mankind. (Takemikazuchi spider tanks -> mundane tanks)

Then entire show focuses on events after the apocalypse, with only a glimpse of flash-backs to earlier events during the apocalypse. But for the most part, the apocalypse itself is largely shrouded.



Are there any details about:


What the apocalypse was?
How did it happen?
What did the pre-apocalyptic world look like?
I'm still learning english, but this is what I understood.


The apocalypse is related to the legend that Yumina describes in chapter 12. It could have been the great war against one angel (it appears on chapter 7 partially, you could see black wings in the windows- this happens when Felicia remember her past). 
The enemy was extremely strong, even a takemikazuchi was not enough to fight against the "angel". I am not sure if it´s an alien or maybe advanced technology from that time. The "angel" uses a laser to destroy a city.
The world look likes today, some buildings without great technology, the only remarkable thing was takemikazuchi. Chapter 7 has more details.