Cosimo’s death in 1464 left the headship of the family to his only surviving son, Piero, who was already middle-aged [Sidenote: Piero de’ Medici and his opponents.] and in feeble health. The five years during which he survived his father are chiefly noteworthy because they witnessed the great split in the Medicean party, which careful observers must have seen for some time to be inevitable. Four of the most prominent associates of Cosimo—Luca Pitti, Diotisalvi Neroni, Angelo Acciaiuoli, and Niccolo Soderini—were unwilling to give to the son the deference which they had shown to the father. Luckily for the Medici, their unanimity did not go far. The first three were actuated by motives of personal ambition, which might easily lead them to quarrel with each other, while Niccolo Soderini was an enthusiast for democracy, and had no desire to humble Piero in order to exalt another in his place. Neroni was the ablest of the leaders, but he was lacking in personal courage, and preferred to employ intrigue and constitutional methods rather than violence. It was only gradually that two parties were organised in avowed opposition to each other. The anti-Medicean party received the nickname of the Mountain, because the great palace of Luca Pitti was rising on the hill of San Giorgio. The residence of the Medici stood on level ground to the north of the Arno, and hence Piero’s adherents were known as the Plain. The first trial of strength took place in 1465, when the opposition made a bid for popularity by proposing to abolish the _balia_ of 1458 and to restore the constitutional method of filling offices by lot. Piero was too cautious to oppose such a measure, and it was carried with virtual unanimity. In November the first draw took place, and Niccolo Soderini became gonfalonier. Disunion among the leaders prevented any use being made of the advantage which chance had given them, and Soderini went out of office at the end of December without having effected any further change in the constitution. In the next year the party strife was extended to foreign politics. Venice had never forgotten or forgiven the part which Florence had played in establishing the Sforzas in Milan. Now that Francesco was dead and succeeded by the more reckless Galeazzo Maria, there was some possibility of evicting a dynasty which was a perpetual bar to Venetian expansion in Lombardy. But to overthrow the Sforzas it was first necessary to overthrow the Medici. And so the leaders of the Mountain made overtures to Venice, regardless of the consideration that a complete reversal of foreign policy might damage the interests of Florence. The Venetians were too cautious to commit themselves to an alliance with a faction which might fail, and moreover they had the Turkish war on their hands. But there was a secret understanding that if Piero de’ Medici were got rid of, either by the dagger or by a revolution, his opponents would be aided by troops under