Lieutenant Colonal Anderson is the commander of the 2nd Rangers Battalion. He gave the order for Miller to go and look for Private James Francis Ryan.
D-day Onwards
On D-day he would of probably have been on the ships away from the battle like most of the commanders of different battalions and divisions.
Shortly after D-day, he ordered Miller to take out towed 88s and three different areas around the villages surrounding the beach. He asks for how many casualties it took to take them to which Miller replied "35 dead times 2 wounded... They just didn't want to give up them 88s" Anderson then replies "it was a tough assignment that's why you got it".
He then calls Miller by his first name almost sympathetically and then proceeds to tell him of another assignment he has for him, which is to find Private Ryan.
This is last and only time he is seen in the film.
Trivia
Anderson wasn't the commander of the 2nd Rangers Battalion. It was actually Lt. Col Rudder.
Anderson is the only person in the entire film that Miller swears in front of. This is shown when he is explaining the mine troubles they faced when trying to flank the enemy. He list several different mines then says after listing a certain mine "the little bastards the mine detectors don't pick". It is unknown why he would swear in front of someone of a higher rank but in front of his own soldiers.