I am looking to better understand how the ranks were closed/dressed in American Civil War infantry units in battle, when casualties are occurring. I was informed that both the front and the rear rank dress to the right and, assuming combat is frontal and the front rank suffers more casualties than the rear rank, that enough men in the rear rank move to the front rank to make both ranks equal again. However, I'm unclear about how the transfer of men from one rank to another occurs. Does anyone have a good grasp of how this process was carried out? I tried researching it online, but instruction manuals don't seem to cover this aspect (or at least I never saw such a topic covered in any of them).
Thanks in advance for any help!