Could the anti-Napoleonic forces have done better by uniting earlier before Waterloo?

Question

During the Waterloo campaign, there were TWO Allied armies facing Napoleon, one under England's Wellington, and one under Prussia's Blucher. Napoleon first defeated Blucher at Ligny, then turned on Wellington's then outnumbered army at Waterloo. The latter was a close battle until the badly wounded 72-year-old Blucher arrived with the remnants of his badly defeated army to reinforce Wellington, late in the day. Then the combined forces crushed the French.

Could the Allies have avoided the defeat at Ligny, and the near-defeat at Waterloo by combining/uniting their forces earlier?

Answer 1

Yes. However, I don't think you are giving Napoleon enough credit here as the driver of events. It appears that the entire point of Ligny was to prevent exactly that. Here's what wikipedia (currently) has to say:

The battle of Ligny is a prime example of a tactical win and a strategic loss. However, had the left wing of Napoleon´s army succeeded in keeping the Prussian army from joining the British Army under Wellington at Waterloo, as the Emperor had planned, Napoleon might have won the Waterloo Campaign.

In particular, it appears that Wellington thought that Napoleon's main aim was going to be to march around him and cut his communications, rather than to separate the allies and defeat them in detail. Napoleon made sure to feed Wellington false intelligence to reinforce this belief.

Answer 2

It was unknown amongst the Allied armies in which direction Napoleon would march. He might have chosen to march into Belgium, which in addition to cutting Wellington off from supply could have led the Belgians to rise in revolt against the Kingdom of the Netherlands, of which they had only lately been forced to become a part. He might have marched on Prussia instead - and I may be wrong, but I believe the Prussian Army had not yet fully concentrated, and so Blucher covered the route between Napoleon and Prussia. In any case, the Allies expected to have to concentrate to fight Napoleon, and their plan was to do so once they knew the axis of his advance. In order to do so, they would have had to have better scouting - and Wellington would have needed greater confidence that Napoleon was not hooking past him at Mons, or at least earlier scouting reports. This is where the battles of Ligny and Quatre Bras come in - the French attacked the Prussians at Ligny, sending them reeling back in retreat, and at Quatre-Bras prevented Wellington's troops from advancing in time to assist the Prussians at Ligny. Having thus cleared the Prussians from his right (as he thought) Napoleon turned on Wellington at Waterloo. Wellington and Blucher (or possibly Blucher's staff, given the injuries he took at Ligny) were in communication throughout the 17th, and so Wellington stood at Waterloo well aware of the fact that Blucher was coming. He had no guarantee that Blucher would arrive in time, but if the Prussians had been forced into a general retreat rather than re-grouping at Wavre, Wellington would have continued retreating. In other words, the course of events clearly shows that Wellington and Blucher intended to force Napoleon to fight them together, and that Napoleon attempted, with incomplete success, to drive them apart so that he could defeat them in detail. So yes, an earlier link-up between the Allied armies would have meant Napoleon's efforts failed earlier.

Answer 3

The Allies knew neither when nor where Napoleon would strike. Quartering troops is an immense strain on both countryside and people, and the Allied armies were disbursed to the greatest extent thought to be compatible with a reasonable concentration time. Concentrating early would have left Napoleon in the advantageous position of just waiting for them to exhaust the capability and tolerance of the nearby populace - at which time not only would they be forced to disburse, but over a much wider area and relatively much further from the direct route Paris to Brussels.

Recall that prior to June 11th, Napoleon's forces were also well disbursed, for the same reason. it was Napoleon's ability to seal the border tight as a drum for three days, while his forces concentrated, that gave him the advantage of surprise.

Second you ignore the considerable effort Napoleon expended both to conceal his concentration prior to crossing the border early on June 15th, but to deliberately mislead Wellington as to the direction of his march. Recall Wellington's comment late on June 15th: "Napoleon has humbugged me, by God; he has gained twenty-four hours march on me." That was no accident.