Johnny commits himself to the Patriot cause at the end of the novel. He decides his future will involve sacrificing for the cause. While Johnny has been slowly emerging into the political realm, he is able to see that the Patriot cause has been fought with “nothing but the guns in their hands and the fire in their hearts.” To a great extent, this describes Johnny, himself. The "fire" in his heart is what enabled him to endure the difficult times and eventually find triumph over them. Like the Patriots, he is, at times, overwhelmed by the condition of the world around him. Yet, he fights and does his duty. In the process, Johnny ends up learning much about the need for action against the British.
While he endures the pain of the Doctor's procedure to help him fire the musket, he understands that the pain of others on the battlefield is far worse. It is in this realization that Johnny makes the decision to fight for Colonists' cause of freedom. He recognizes that in their struggle lies his own. The mirroring of enduring, scraping through difficulty, and eventually triumphing becomes the parallel story for both the Colonists and Johnny Tremain.