How does Henry come into possession of the flag?

Henry and Wilson overhear an officer say that their regiment fights like "mule drivers". Determined to prove them wrong, Henry and Wilson fight really hard. In the ensuing battle the flag bearer falls and Henry proudly picks it up. Because he has fought so well, Henry gets to carry the flag into the next battle. Although they win this battle, Henry regrets certain things he has done, in particular the way he had treated the tattered man.