He had no way of signaling his orders - the only signals given at Waterloo were by officers waving their hats.

From Waterloo A Near Run Thing by David Howarth. Page 57. Fascinating the practices and constraints of a different time.

These extended lines were also the best defence against long-range artillery, in so far as a cannon shot passing through them was unlikely to kill more than two men. But they were powerless to stop a cavalry charge, and on the word ‘Prepare to receive cavalry’, the infantry formed hollow squares, three ranks deep, the outer rank kneeling with the butts of their muskets resting on the ground and the bayonets pointing up and outwards. A steady square, which quickly closed whatever gaps were shot in its ranks, could not be taken by cavalry, largely because the horses, having wills of their own, could not be made to charge the hedge of bayonets. A square was also the strongest psychological forma­ tion. There was somebody guarding your back, and you could not run away except by running out of the companionship and comparative safety of the square, and into the danger outside it.

Squares were mainly defensive. But cavalry could also be defeated, either by grape or canister shot from artillery, or by other cavalry: a cavalry force which maintained its ranks was always stronger than one which had lost its cohesion under fire.

In a standard attack, the artillery first opened fire, a long- range and more or less indiscriminate bombardment to dis­ organize the enemy, and the skirmishers also advanced with the same intention. Then the infantry marched forward, holding their fire until the last few paces from the enemy line. They were often accompanied by horse artillery, which stopped to fire and then galloped on again. After firing their muskets, the infantry charged with the bayonet, and there was a crucial moment when the cavalry should arrive — after the front line of the enemy’s artillery was overrun, and before his infantry had time to form squares. With that exact timing, the battle was as good as won: the cavalry slashed the enemy line to pieces, and the infantry marched through it. But of course it was seldom so simple. If the enemy infantry held on a little longer than expected, his artillery might still be free to use its grape and canister on the cavalry; and if the cavalry became disorganized, the enemy cavalry, still in its ranks, was also given a moment when it could counter-charge and suddenly turn the tide.

A field commander’s first need, especially in defence, was therefore a steady and disciplined infantry, who would maintain their ranks whatever happened. His second need was a sense of tactical timing. And this implied a sense of anticipation, because he had no way of signalling his orders - the only signals given at Waterloo were by officers waving their hats. He had to send his orders, verbally or in writing, by mounted aides-de-camp. At best, they took an appreciable time to deliver them, even within the limits of the battlefield, and at worst they might be unhorsed or wounded or killed on the way, or simply get lost in the melee and fail to find the man the orders were addressed to.

All this was common knowledge among the hosts of men. And there was one other thing so deeply imbedded in their consciousness that one must take account of it. This was their reverence for their regimental colours. Standards no doubt began in armies far back in history simply as rallying points, to help soldiers who were lost among the crowds on battlefields. But just as uniforms had evolved from mere utility until they were symbols of masculinity and bravery, so standards evolved to symbolize what men believed they were fighting for. The colours in all armies were presented to the regiments by their Sovereigns in solemn ceremony, and so became precious tokens of patri­otism and regimental pride. They were also blessed by priests, and when they were honourably shot to pieces the tattered remains were sewn on to nets and hung up in cathedrals. So they were given a holy significance, too. To lose its standard to the enemy was a disgrace which could haunt a regiment for a whole generation: to defend it, men cast away their lives: to capture an enemy standard was every good soldier’s ultimate ambition, the height of his concept of glory.