19th-century adversary of an 18-Down Crossword Clue

 The answer to the crossword clue "19th-century adversary of an 18-Down" is Cavour.

The 18-Down clue is "King of Italy 1878 to 1900", and the answer to that clue is Umberto I. Cavour was a 19th-century Italian statesman who played a key role in the unification of Italy. He was a rival of Umberto I, and they had a number of disagreements about the direction of the Italian government.

Cavour was born in 1810 and died in 1861. He was a member of the Piedmontese nobility, and he studied law and political science. He entered politics in the 1840s, and he became a leading figure in the movement for Italian unification.

Cavour was a strong supporter of a united Italy under the rule of the Piedmontese monarchy. He believed that this was the best way to achieve Italian independence from Austria and the other foreign powers that controlled parts of Italy.

Cavour was a skilled politician, and he was able to maneuver the Piedmontese government into a position of strength. He negotiated alliances with France and Britain, and he used these alliances to defeat Austria in the 1859 war.

After the war, Cavour was able to push through a referendum that unified most of Italy under the rule of the Piedmontese king. He died shortly after the unification was achieved, but he is remembered as one of the most important figures in Italian history.

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