Antagonist
Character Role Analysis
The Bomb/War
Even though the U.S. is responsible for dropping the bomb, that country is not universally portrayed as the Big Bad Wolf in this book (although Hersey makes frequent references to people like Mr. Tanaka and Mrs. Nakamura, whose patriotism seems rooted in anti-American feelings). In fact, Dr. Fujii and Mr. Tanimoto are portrayed as actually being pretty pro-American.
Mr. Tanimoto, for example, threw himself into peacekeeping efforts by traveling to the U.S. and appealing to its residents in churches across the country. They weren't the enemy, to him; rather, war and the threat of nuclear attacks were, and he turned to American citizens for help in combatting those evils.