while on the march, in what way does the regiment lose the look for new recruits?

From the text;

"It was during this rapid march that the regiment lost many of the marks of a new command.

The men had begun to count the miles upon their fingers, and they grew tired. "Sore feet an' damned short rations, that's all," said the loud soldier. There was perspiration and grumblings. After a time they began to shed their knapsacks. Some tossed them unconcernedly down; others hid them carefully, asserting their plans to return for them at some convenient time. Men extricated themselves from thick shirts. Presently few carried anything but their necessary clothing, blankets, haversacks, canteens, and arms and ammunition. "You can now eat and shoot," said the tall soldier to the youth. "That's all you want to do."

There was sudden change from the ponderous infantry of theory to the light and speedy infantry of practice. The regiment, relieved of a burden, received a new impetus. But there was much loss of valuable knapsacks, and, on the whole, very good shirts."