WHAT SLENDER BILLY DID (the long version):
In AIA Colonel Audley, while describing the skirmish at Quatre-Bras, tells Worth, "Oh, Halkett galloped forward to the front with one of his A.D.C.s, saw a corps of cavalry forming, and of course returned at once to his brigade, and gave the order to form squares. The 69th - that's Colonel Morice's regiment - were in the act of doing so when up came Slender Billy, and wanted to know what the devil they were about. 'Preparing to meet cavalry' - 'Oh, cavalry be damned!' says Billy. 'There's none within five miles of you! Form column, and deploy into line at once!' Morice had no choice but to obey, of course. The regiment was actually engaged on the movement when about eight hundred Cuirassiers came charging down on the brigade. The 30th and the 33rd were firmly in square, but the Cuirassiers rode right through the unfortunate 69th, scattered the Belgian and Brunswick cavalry, got as far as Quatre-Bras itself, and completely turned our position. If it hadn't been for the Duke's directing the 92nd Highlanders himself, God knows what might not have happened!" Morice and scores of others were killed.

Later on (on the 18th) the narrator in AIA tells us, "Ompteda, knowing that they [the French tirailleurs] were strongly supported by cavalry, sent back this intelligence to his General [Alten], but the Prince of Orange, carried away by the excitement of the moment, and forgetful of the disaster attendant upon his interference at Quatre-Bras, impetuously ordered him to advance at once. Ompteda looked at him for one moment; then he turned and gave the command to deploy the 5th Line battalion of the Legion. Placing himself at its head, he led it against the French skirmishers, and drove them back. The Cuirassiers in support charged down upon him; he fell, and half his men with him, cut to pieces by the cavalry." Fortunately Slender Billy was eventually wounded in the arm and carried off the field before he could do more damage (Cornwell, in his Sharpe series, actually has Sharpe shoot the Prince of Orange to get him off the field). The Dutch later built a monument to the wounded prince, the Butte de Lion (sp.?), a giant hill topped with a lion, which is placed smack on the front line at Waterloo, and towers several stories high. You can climb up stairs to the top and get a lovely view of that portion of the battlefield that is not covered by the monument.

WHY IT WAS STUPID
Infantry while in line formation or advancing, should not face cavalry because the cavalry (being mounted on horses) moves faster and has superior height and can easily get in behind the infantry and cut every man down, even if the men on foot have superior numbers. But the Allied infantry could form square to defend against cavalry. This means they would form a giant square, ideally three or four men thick, with bayonets facing outward. As long as the square held, it would be impossible for the cavalry to get in behind and cut everyone down. Horses would refuse to charge straight down bayonet points to break a square, so squares were usually only broken if a wounded or disoriented horse unwillingly fell against the square and cavalry got inside before the hole could be patched up, if the men in the square panicked and ran, or if the cavalry killed men in the square through hand to hand combat until there were not enough men left to form a square. Maitland's squares at Waterloo had so much French cavalry riding around them that the allied troops couldn't even see their own squares for all the horses. Most of the squares held however, though in many cases, the English were left standing dead in a square. Mary and Vidal's grandson Harry was killed defending one of Maitland's squares.

Troops in line (as opposed to square) were much better for facing other infantry, because in line formation they could easily advance or retreat, and could fire more bullets in the same direction. Anyway, I hope that's clear.

WELLINGTON'S BED
Alexander Gordon died in Wellington's bed at the in at Waterloo following amputation of his leg. An answerer pointed out: as is said at the end of Chapter 24 this obviously had a great effect on the Duke for the "Marshal Prince could call the battle what he liked (Belle-Alliance) but his lordship would head his despatch to Earl Bathurst: "Waterloo".

Actually I (the challenger) believe, unlike poor Gordon, Uxbridge survived the amputation of his leg. The farm La Haye Sainte and the chateau of Hougomount are the most well known buildings, of course, because they were most strategically important. La Belle Alliance was the farmhouse Napoleon set up his headquarters in, and while it was visible from the front line, it was not on it.

WELLINGTON WEATHER
Rain! In AIA (the night of the seventeenth) Baron Muffling tells the Duke the rain is still very bad and that the ground is a morass in many places. "'My people call this sort of thing Wellington weather,' observed... [Wellington], 'It always rains before my battles.'"

And an answerer points out: Have you ever considered how much of an advantage a muddy field was for the army that was on the defensive (as Wellington generally was)? Maybe God was on his side.