He fortified Lucca, and prepared to invade Florentine territory. The Florentines sent a strong detachment of troops into Lombardy on condition that in the following summer the Genoese and other Guelfic powers were to attack Lucca on every side and annihilate the rising power of Castruccio. Scarcely had an army been assembled for this purpose, when intelligence arrived that their principal condottiere, Jacopo di Fontanabuona, had passed over with all his following to the enemy; he had been commissioned to make himself master of Buggiano and other places by treachery, but failed, and soon after joined Castruccio with two hundred men-at-arms. Castruccio with this reinforcement and the possession of his enemy’s secrets crossed the Gusciano on the 13th of June, 1323, attacked Fucecchio and other places, ravaged the surrounding country, then passed the Arno, devastated the territory of San Miniato and Montepopoli with all the vale of Elsa, and marched quietly back to Lucca. On July 1st he suddenly reappeared in front of Prato, only ten miles from the capital, with six hundred men-at-arms and four thousand infantry; the citizens sent in terror to Florence for help, but paralysed by Fontanabuona’s treachery she was nearly destitute of regular troops. The citizens however had not quite forgotten the use of arms, and their spirit was still high; the shops were immediately closed, a candle was placed at the Prato gate, and every individual liable to serve summoned to the ranks ere it burned out, under the penalty of losing a limb; a proclamation being issued to announce that all exiles who instantly joined the army would be pardoned and restored to their country. By these prompt measures, twenty-five hundred men-at-arms and twenty thousand infantry were in the field round Prato on the 2nd of July, only one day after Castruccio’s appearance, four thousand of whom were exiles! [Sidenote: [1323-1324 A.D.]] Castruccio’s rash advance with so small a force might have ended disastrously if the Florentines had been well commanded; but he retired in the night and made an unmolested retreat to Serravalle, the discord in the Florentine camp, an offset from civil dissension, having saved him. Thus ended this singular campaign in which the army scarcely saw an enemy, but which brought back danger and revolution to the state. The Florentines now added three subalterns (_pennoniere_) to each urban company, so that the whole force became infinitely more flexible and divisible and better adapted to real service.