france had a monarchy until the french revolution in 1789. king louis xvi and his wife, marie antoinette, were executed in 1793. thousands of other french citizens were killed. napoleon bonaparte took control of the republic in 1799. he later made himself emperor of the first empire (1804–1814). his armies conquered most of continental europe. the metric system was invented by french scientists during the french revolution. that time 3 estates were developed.