“Effective characterization” means that the author has created characters who seem like real people rather than stereotypes. Each individual has enough specific features to make them memorable, but their actions are plausible rather than far-fetched. When multiple characters are placed in an extreme situation, such as war, their behavior may change radically, or they may readily adapt to the difficulties they face. The characters’ traits matter in the plot because specific aspects influence the behavior of others, thereby shaping the outcome.
In The Machine Gunners, Chas is the protagonist who links two different sets of characters, his family and his friends. Robert Westall makes Chas credible because the boy displays typical adolescent behaviors, such as dissatisfaction with his parents, but he also engages in distinctive actions to try to cope with the war. In that regard, his relationships with his friends in obtaining the machine gun take on greater significance than those with his parents. For the children, their partial understanding of the wartime situation leads them to make some wrong choices, which give momentum to the plot; those choices, however, are consistent with the personality of each one.
Several of the adults embody the wartime stress as an actual person would likely experience it. Chas’s mother, for example, is concerned with the food rationing and shortages, as were most people, but she is notable for her extreme obsession with the material aspect. Mr. Liddell, the school teacher, embraces his wartime role, perhaps because he felt he had not lived up to his duty before he became a Home Guard. He connects his duty with his treasured uniform.