The discontinuance of a nonconforming use for a period of one year shall be regarded as permanent abandonment, and, thereafter, the land, building or structure where such nonconforming use previously existed shall be used and occupied only in conformity with the regulations prescribed by this chapter for the district in which such land, building or structure is located. Intent to resume active operations shall not affect the foregoing, except that the provisions of this section shall not apply where such discontinuance is directly caused by war, strike or the construction of a public improvement by a governmental agency.