The Sterilization Operation was a military operation to destroy Raccoon City to eradicate all traces of the t-Virus.
On September 23, 1998, a modified ε strain of the t-Virus contaminated Victory Lake, an important reservoir in Raccoon City. The US Army and Army National Guard formed a blockade outside the city limits to prevent the spread outside Arklay County. When a conventional military solution to the outbreak proved ineffective, plans were put in motion to totally destroy the city. On the early hours of October 1, after some deliberation, the federal government conceded to a Congressional committee's demands and the President ordered that an experimental thermobaric missile should be launched at the city.[excerpt 1] The city was destroyed at daybreak, killing infected and uninfected civilians and soldiers who failed to escape.
The federal government continued to cover the existence of the t-Virus and B.O.W.s up reported in the incident to avoid being implicated in Umbrella's bio-weapons development project. As a result, the death toll from the bombing was estimated based on the city's actual population - 100,000. The unexplained act of aggression toward the US citizens led to the President resigning in disgrace. A similar bombing took place in 2013 with the destruction in Tall Oaks to end a C-Virus outbreak, but was more readily justified as the existence of mutagenic viruses became common in knowledge.
The English localizations refer to both operations as "Operation: Bacillus Terminate". However, that name does not appear in the original scripts, so is to be treated as non-canon.
Though the games themselves make no mention as to the weapon's nature, Yasuhisa Kawamura clarified in Conquest of Nemesis that it is not a nuclear weapon and thus leaves no radioactive trace,[excerpt 1] although Resident Evil Archivesstates the missile was nuclear.
↑ 1.01.1Excerpt from Conquest of Nemesis, p.350: Q19. エンディングに出てくるミサイルはどのようなもの？ A19. 核兵器につぐ威力を持つ、 気化爆弾などの新型爆弾のひとつで、 詳細は不明ですが、 放射能汚染はきわめて低いようです。 この物においては、 レールキャノンと並ぶ米軍最大の秘密兵器と言えるでしょう。