Although neither Karl Marx nor Friedrich Engels described how archaeology could be understood in a Marxist conception of history, it was developed by archaeologists in the Soviet Union during the early twentieth century. Becoming the dominant archaeological theory in that country, it was subsequently adopted by archaeologists in other nations, particularly the United Kingdom, where it was propagated by influential archaeologist Gordon Childe. With the rise of post-processual archaeology in the 1980s and 1990s, forms of Marxist archaeology were once more popularised amongst the archaeological community.