I consider June 5th to be the beginning of the military operations of the Waterloo campaign. One may quibble and suggest earlier, but it certainly cannot be later. It was on this day that units destined to fight in the campaign began to concentrate on the frontier.
This complex and brilliant concentration was actually on the simple side as maneuvers go - and the execution was a complete disaster. How many times have you read that in a history of the campaign?
The reason you have not is because the vast majority of histories of this campaign, in any language, ignore the concentration. I count only 3 that examine the events in detail - Lettow-Vorbeck, Callatay, and de Wit. Regnault and Houssaye both edit out key events for reasons unknown, though Callatay believes it was to protect Soult and suggests Grouchy protected Soult as well. (It is a fact that Houssaye protected Du Barail - living relative was in government, and Soult's descendents were still personalities in France at that time of his writing.)
All the other histories of French operations during the Waterloo campaign are conspiracy theories. I base this on reading an article someone posted here by Micahel Sibalis, "Conspiracy on St. Helena?" I found it very compelling, like this:
The conspiracy theoristsí way of constructing a historical argument demonstrates their fundamental misunderstanding of the historical method. They raise doubts about an established interpretation and construct new hypotheses based on (often minor) inconsistencies in the historical record, while usually ignoring or dismissing the overwhelming evidence amassed by professional historians.
The conventional history of French operations during 1815 ignores (or frequently dismisses) the overwhelming evidence - and the most significant events of the campaign are lost: Napoleon's orders were changed, intelligence was withheld, treason has been downplayed, Napoleon's recall orders to Grouchy the night of June 17th are declared lies, etc. etc .etc - yet these positions have little evidence to support them.
On Napoleon1er.org, they are "blogging" each day of 1815. I am also blogging the campaign, and starting to day will be posting once or more daily with all the key events that the conventional history would like to ignore in its race to June 18th.
If there is interest, I'd be happy to post the events of each day here. I have collected the overwhelming evidence all meticulously sourced.