相互 そうご確証 かくしょう破壊 はかいではありませんでした
sō gokakushōwa kaidewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 相互確証破壊

1. Was not mutual confirmation destruction.; Was not reciprocal verification failure.

Past/Perfective
Negative
Polite
Formal Register