Why did soldiers march in rows in the old days?

Answer 1

Back then they used to have different ways of fighting. They used to line up and just shoot at each other in lines. Now they use different ways of fighting that do no include lining up and firing at each other

Answer 2

Different types of marches were used for different situations. A parade march was made to show the army as attractive, orderly, and well-disciplined. Other marches were used to get the army from place to place, to speed up deployment, or to cross a bridge.

One basic purpose of all marching is to make the men feel like part of a larger structure. There is much less panic if everyone around a person is doing exactly the same thing.

In some cases the well-trained marches seemed to work against the soldiers. In Pickett's charge in the last day of Gettysburg, the men marched in straight rows right up to the center of the Union line. Hundreds upon hundreds were cut down by muskets and cannons.