Hi, the hotel I was staying in was a few streets away from le sacre coeur and the information you provided was very interesting, did not know the history of that area. That was a very short lived revolution!
Short, but the first red flag, and the first "communist" revolution, according to ... Karl Marx

A question, around that area I saw many armed police (soldiers?) with sub machine guns doing patrols. Why is this? I once got accosted by a peddler in that area which was uncomfortable but I cannot imagine armed soldiers are there to control that issue?
This is a really touristic area. So there's a lot of people that gonna accost you, mainly to propose you to enter for a sex show

. No reason for military with them

. But, for decades now, they try to frightened us by the terrorist menace, and a special emergency state is declared so that they can display military in Paris. As far as I know, their machine guns are not even loaded (an ex military told me that), so it's not even to really protect people, but just to cause fear in the population, to be able to manipulate the opinion more easily. This is exactly "
the shock doctrine" (if anybody on this forum haven't seen that and read this, it's an emergency, grab it and watch it, or read the book

).
It was so cold in Paris I think I have returned to the uk with a dose of pnumononia and have been bed bound. Still, was worth it for the amazing gig! 
I can't believe that someone living in the UK could find Paris colder than England

[edit] about the military, Wikipedia is definitely the place to look for
here's a very brief english page about it and a
more complete page, in French, where you can see that it has been cancelled only two times since 1991, once for 4 years, and once for 2 month, and was never really canceled since 1996 ...