With British Hanover's defeat in the Napoléonic Wars the short-lived Kingdom of Westphalia annexed the Duchy of Bremen in 1807, including Zeven, before France annexed it in 1810. In 1813 the Duchy was restored to the Electorate of Hanover, which - after its upgrade to the Kingdom of Hanover in 1814 (and still ruled in personal union with the United Kingdom of Great Britain and Ireland) - incorporated the Duchy in a real union and the ducal territory, including Zeven, became part of the Stade Region, established in 1823. In 1824/1825 Carl Friedrich Gauß carried out the trigonometric geodetic surveying of the Stade Region, as commissioned by King George IV of Hanover and the United Kingdom. Gauß used the tower of the Lutheran Church of St. Viti as a benchmark for his triangulations.