After the collapse of Napoleon III's French army at the Battle of
Sedan at the beginning of September, Prussian forces begin to
besiege Paris.
Citation:
Editors. "Siege of Paris by Prussian forces begins".
The Literary Encyclopedia. First published 30 December 2011
[http://www.litencyc.com/php/stopics.php?rec=true&UID=18583, accessed 26 May 2013.]