To this day, no one really knows what WW I was really about?

So when this event takes place:

http://timesofindia.indiatimes.com/world/europe/French-German-leaders-pay-emotional-tribute-to-World-War-I-fallen-soldiers/articleshow/39559031.cms

what on earth are they actually commemorating?

Those who have no basis to grieve are the most voluble re those who died for nothing.