When you see a movie about the 1700s or early 1800s, you see soldiers walking slowly towards each other in bright uniforms, standing in lines, and firing. It looks suicidal. But there was a terrifying logic to it.
It all comes down to the weapon: the smoothbore musket. This gun was wildly inaccurate. If you aimed at a man 50 yards away, you’d probably miss. The only way to hit anyone was to mass your firepower. A single soldier shooting was useless. But 500 soldiers standing shoulder-to-shoulder, firing at once, created a wall of lead. Even if they weren’t aiming, the sheer number of bullets would hit something.
So why didn’t they hide behind rocks? Because of the other weapon: the cavalry. If you spread your men out behind cover, you lost your concentrated firepower. A group of cavalry could then charge your scattered soldiers and ride them down. The line formation was the only defense against cavalry. It presented a solid wall of bayonets. You stood in a line to protect yourself from being trampled by horses.
It was a game of rock-paper-scissors. Infantry line beat cavalry. Cavalry beat infantry square. Artillery (cannons) beat infantry line. And infantry in a line beat artillery (if they could get close). Moving in formation, with drums beating, wasn’t just for show. It was the only way to keep hundreds of men together as a single, functioning weapon. It was terrifying, but it was the science of war at the time.