Japan, the bomb was dropped at Hiroshima and Nagasaki.
According to History it was a kamikaze. Japanese for divine wind. Works of fiction say it was hurricane or typhoon. But I would not call that a person.
The war was actually super significant, and there wasn't a singular person that actually prevented the conquest. To my knowledge anyway.
Answer: It was this pan-Slavic nationalism that inspired the assassination of Archduke Franz Ferdinand in Sarajevo in June 1914, an event that led directly to the outbreak of World War I
Answer: German machine guns
Explanation:
German machine guns were the most effective defensive weapon during the Battle of Passchendaele, working in tandem with bunkers, barbed wire, and positions higher than the attackers'.