In The Boy in the Striped Pajamas, how does the story of Bruno and Shmuel embody heroic qualities?

In their willingness to go on an adventure, donning "armor," and in their spirit of sacrificing for one another, Bruno and Shmuel embody heroic qualities.
The hero must embrace adventure.  We tend to valorize people as heroes when they undertake something that most of us could not.  Bruno and Shmuel fit this pattern when they decide to take one “final adventure.”  Both boys are dismayed when they realize that Bruno will be leaving for Berlin.  In order to commemorate their friendship, they decide to take a  “great adventure." Bruno and Shmuel are heroes in the way they fearlessly embrace the spirit of adventure.
Heroes have to don "armor" as a part of their adventure. The hero has external clothing which represents the their quest.  In Bruno's and Shmuel's case, it would be the "striped pajamas," or the uniform that prisoners had to wear in Auschwitz.  Bruno sheds his "civilian" clothes as he crosses under the fence and wears "the striped pajamas."  At this moment, both boys are ready to go on their quest.  Even though, Bruno realizes that the clothes do  “not smell very nice,” he sees the clothes as a part of his adventure.  Like a hero, he remembers the words of his "sage" grandparents who told him that "You wear the right outfit and you feel like the person you’re pretending to be."  Bruno and Shmuel are heroic in how their clothing, their "armor," represents their quest.
Heroes inspire because they sacrifice so much for others. This heroic quality is seen in Bruno's and Shmuel's journey.  Bruno has second thoughts about his quest when he sees the people on the other side of the fence "looking horribly sad.”  While he wants to abandon his initial commitment, Bruno is heroic when he realizes that he would be forsaking Shmuel.  He does not want to let his friend down.  Bruno is heroic in the way he sees something more than himself at stake.  He continues his quest because of it. When Bruno and Shmuel are in the gas chamber, unaware of what will happen, Bruno reminds him that they will be "best friends for life."  Bruno and Schmuel die in the gas chamber, having undertaken an adventure and shown unwavering commitment to their friendship.  In this way, their heroism lies in how they sacrifice for something larger than themselves.