Most important people or entities in "Band of Brothers"

There are many important characters and entities in the book "Band of Brothers." Each soldier in E-Company provides a certain detail to the book. For example, many soldiers in the Company will talk of their Captain, who goes by the name of Sobel, and how he would occasionally abuse his authority over the Company. Even though he was a high ranking officer, it was said that Sobel was not the most intelligent during combat situations. Most of the men in E-Company would ignore Sobel's commands, and retalliate against him in a friendly manner later. Another character with some history is Harry Welsh. This soldier was a reluctant officer, and after jump school was promoted to sergeant. He was demoted to private three times, all accounts for fighting. Welsh was a tough Irishman with obvious leadership potential. For this, he was assigned to Easy Company, 2d Battalion, 506th PIR.