Mitre took up arms again. Hoping to prevent Avellaneda's 12 October inaugural, he mutineered a gunboat; he was defeated, however, and only President Avellaneda's commutation spared his life. Following the 1890 Revolution of the Park, he broke with the conservative National Autonomist Party (PAN) and co-founded the Civic Union with reformist Leandro Alem. Mitre's desire to maintain an understanding with the ruling PAN led to the Civic Union's schism in 1891, upon which Mitre founded the National Civic Union, and Alem, the Radical Civic Union (the oldest existing party in Argentina).