At the end of the novel, Johnny is standing on Lexington Green waiting for Doctor Warren to prepare his surgical instruments for the operation that will repair Johnny's hand at least enough for him to be able to fire the musket Rab left him. He is looking around at all the people and things he sees, reflecting that, "This was his land and these his people" (12.5.49). Finally, he remembers James Otis's words and remembers that Rab has died, and others will die, simply so that "A man can stand up" (12.5.60).
There's a lot of torch-passing going down here. Johnny is standing on Lexington Green, the site of the first shots of the American Revolution and where Rab fell, waiting for a surgery that will enable him literally to pick up Rab's musket and take Rab's place. But it doesn't end there. Johnny looks into the future and sees that someone will always be there to pick up the torch, to fight so that "A man can stand up" (12.5.60): "Please God, out of this New England soil such men would forever rise up ready to fight when need came. The one generation after the other" (12.5.54).
Writing for a nation in the midst of World War II, Forbes may have intended the reader to pick up Rab's musket along with Johnny, to experience through him a connection to the American past.