As long as the oligarchical government was successful, there was little prospect of its overthrow, but from 1421 its credit steadily declined. The reunion of the [Sidenote: War with Filippo Maria Visconti.] Milanese territories under Filippo Maria Visconti constituted a serious menace to Florence, and the imperative duty of self-defence compelled the republic to embark once more in a desperate struggle for existence. In 1424 the Florentine army, under Pandolfo Malatesta, was defeated with great loss in the battle of Zagonara. A despairing appeal was made to Venice for assistance, and the intervention of Carmagnola saved Florence from annihilation. But the spoils of victory were monopolised by Venice, and the aggrandisement of their ally was by no means popular with the Florentines. The power of the oligarchy had rested upon the success of their foreign policy, and alarming discontent was the inevitable result of an unsuccessful war. Two important measures were resorted to in the hope of restoring the prestige of the dominant faction. The heavy expenses of the war had called attention to the old grievance of arbitrary taxation, and in 1427 a reform was introduced to provide a more [Sidenote: The Catasto of 1427.] equitable basis of assessment. According to Machiavelli, the acceptance of the _Catasto_, as it was called, was due to the influence of Giovanni de’ Medici. Every citizen was to report to the gonfalonier of his district his whole income from every source; and concealment was to be punished by confiscation. From fixed capital the income was to be estimated at seven per cent. These reports were to be collected into four books, one for each quarter of the city; and henceforth the assessment of taxation was to be determined by them instead of depending upon a man’s political position and opinions. As wealth fluctuated rapidly in a mercantile community, a new _catasto_ was to be made every three years. It was a notable sacrifice on the part of the ruling clique, and probably tended to weaken their unanimity, but it helped to pacify public opinion for a time. Rinaldo degli Albizzi now came forward with a new scheme for restoring the credit of his party. Ever since the days of [Sidenote: Attack upon Lucca, 1430.] Castruccio Castracani, the annexation of Lucca had been a darling object of Florentine ambition. Lucca was, at this time, ruled by one of its own citizens—Paolo Guinigi—who had sided with Milan in the recent war. Rinaldo proposed to treat this as a pretext for attacking Lucca. It was in vain that Niccolo da Uzzano pointed out the risks of the enterprise. Giovanni de’ Medici was dead, and his son Cosimo supported the proposal of Rinaldo. His conduct on this occasion has exposed him to the suspicion that he foresaw the failure of the enterprise, and was willing to ruin his opponent even at the expense of the state. War was declared in 1430, and Rinaldo degli Albizzi was