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The resistance is attacks the Starkiller Base with what appears to be pretty small time ammunition even by modern earth missiles, which requires a long running sequence of repeated flybys. The objective, IIRC was to destroy a critical piece of machinery on the surface which would then destabilize the entire planet/weapon (feel free to correct in edit if I remember incorrectly). OK cool, but then why the force wouldn't they just drop a nuclear bomb on it? Have nuclear weapons been used any other time in Star Wars (including EU), or, like smart phones, have they just not been invented in that world?