Cavalry were the "eyes of the army"

I may just be showing my ignorance here but I read something pretty dang interesting in Gods and Generals, Jeff Shaara's terrific book about events leading up to the Battle of Gettysburg in the American Civil War. He mentioned at one point how the cavalry was "the eyes of the army," which I had no conception of, but which makes a lot of sense when you think about it.

We're talking zero electronic communications back then, when Indian smoke signals were probably about as advanced as anything the white men had. So you've got all these armies walking wherever they went and a much smaller band of soldiers on horseback who could cover a lot more ground. They' go out and poke around and go riding back with whatever they've learned.

Here's a bit I found on a website:

The cavalry were the eyes of the army. They traveled in the rear area of the enemy where they searched for information about the enemy force. Also, they captured enemy officers and men whom they took away as prisoners for questioning . . . When a cavalry unit became engaged they usually broke off contact at once and rode away. The advantages of the cavalry were: 1) they could search the enemy's area to learn their strength and location and, 2) they could screen their army's size and location from the enemy.

I'm sure a lot of you with military experience yawn about this, because it's old hat. But I never knew this before and now I do. And if you didn't know it before, you do now.