100 years ago today,  Austria-Hungary declared war on Serbia, after rejecting Serbia's conditional acceptance of the July Ultimatum.  This is often called the official start of the First World War, though Germany wouldn't declare war on Russia until 1 August.

 

I thought I'd post these composite photos from London.  1914 and 2014:

 

http://www.dailymail.co.uk/news/article-2707568/First-World-War-photos-soldiers-marching-streets-superimposed-modern-day-images.html

Nicely found, those are the best composites I've seen yet.  It's amazing how 100 years ago doesn't seem that far away with all the photos and simulators out there.

In Flags held high, those can't be Japanese flags?

They are.  Japan declared war on Germany after Germany refused to give up it's Asian territories to China:

 

http://en.wikipedia.org/wiki/Allies_of_World_War_I#Japan