Its essential purpose was as a tool of the Valencian nobility to be used against the influence of Catalans and foreigners on the actions of the Crown.
By 1285 the Unions had severely curtailed the powers of the king and were hindering his efforts in the War of the Sicilian Vespers and against the Aragonese Crusade that invaded Catalonia that year.
The Union persuaded Ferdinand, Prince of Aragon to be their lieutenant-general and, with an army of 30,000, he dealt the royalists a second defeat.
When he had again obtained the upper hand, Peter ordered the "great bell" that had been used to rally the Unidos to be melted and its liquor poured down the throats of the Union's leaders.
[3] On 1 November 1348, the Union attacked the Jews of Morvedre because they, being by law serfs of the Crown, were considered de jure royalists.