A crude single-shot handgun developed by the United States during World War II. Cheap and quick to mass-produce, it was meant to be air-dropped in large numbers to insurgents in Axis-occupied areas, for use against the occupation forces.
With its single-shot capacity, poor ergonomics, and unrifled barrel (with consequently short range and sub-par accuracy), each Liberator was expected to be used only once; it would then presumably be discarded in favor of the newly-deceased occupier's weapon. The OSS was famously unenthusiastic about the FP-45, preferring to distribute "proper" weapons, and though many were distributed, few records exist of Liberators actually being employed in the field.
This tag implicates handgun (learn more).